A

ATP    (adenosine  5'-  triphosphate):   nucleotide   triphosphate composed  of adenine, ribose, and 3 phosphate groups that is  the principle  carrier of chemical energy in cells. The recycling  of ATP  within  the  cell allows the body  to  function  without  an enormous daily intake of food.

Acetylation: the process of adding or subtracting acetyl molecules used to activate or inactivate the expression of genes.

Acid :Any chemical compound that releases a hydrogen ion (H+) in aqueous solution, thus rasing the relavite concentration of protons. It results in a decrease in pH of the solution.

Action  letter : an official letter from the FDA to a NDA  or  BLA sponsor that informs of a decision by the agency.

Active immunity: a type of acquired immunity whereby resistance to a disease is built up by either having the disease or receiving a vaccine to it.

Active site: the site within the three-dimensional structure of a protein that is responsible for specific molecular associations and transformations.

Acute phase: a short, sharp, and relatively severe course of a disease; not chronic.

Adaptive immunity : part of the immune system that recognizes previous contact with a specific microbe and directs its defense against that specific invader with T-cells and B-cells. Also known as acquired immunity.

Adenine : a nitrogenous base. One of the four bases that makeup DNA. It pairs with thymine (T).

Adenocarcinoma: a cancer that develops in the glandular lining of an organ. More than 95% of prostate cancers are adenocarcinomas.

Adhesion   molecules :  molecules  that  facilitate   cell-to-cell communication. They are active in such processes as wound healing and tumor metastasis.

Adiposity  rebound :  the  normal pattern of  weight  gain  in  an infant,  followed  by weight loss as a young child and  then  the point at which weight gain flattens out. The earlier the  rebound the greater the risk of adult obesity.

Adjuvant :  an insoluble substance that is injected along with  an antigen to increase an immune response.

Adoptive  immunotherapy:   the activation of select  immune  cells outside  the  body followed by reinfusion of the cells  into  the patient.

Adrenal glands: two glands located above each kidney. They produce several kinds of hormones, including a small amount of sex hormones.

Aerobic : needing oxygen for growth.

Affinity  chromatography :  a technique for separating  cells  and molecules--   particularly  proteins  and  DNA--   from   complex mixtures. It was first introduced in 1968.

Agonist : a molecule that activates receptors.

Alleles: alternative forms of a genetic locus. A single allele for each locus is inherited separately from each parent.

Allogenic: of the same species, but with a different genotype.

Alpha interferon: a member of the family of proteins  (cytokines) released  by leukocytes (white blood cells). Among  its  multiple regulatory  functions is to interfere with  viral  multiplication and with proliferation of cancer cells.

Alternative splicing : the process whereby the splicing pattern is able to determine different products from the same RNA molecule.

Amino  acids: the building blocks of proteins that are joined together by peptide bonds to form a long chain, or polymer. Each of the 20 distinct  amino acids, in some particular sequence of 100 or more, construct  all cellular proteins.

Amplification : an increase in the number of copies of a  specific DNA fragment, in vitro or in vivo.

Amyloid :  a generic term used to describe proteins that form  so-called  beta-sheets,  which  fold in a  particular  way  to  form insoluble  deposits. A number of brain disorders associated  with dementia are linked to amyloid, including Alzheimer's.

Analogs : chemically related structures.

Anaerobic : growing in the absence of oxygen.

Androgens: male sex hormones produced by the testicles and, in small amounts, the adrenal glands.

Aneuploidy : the duplication of one or more chormosomes. This type of chromosomal abnormality is found in nearly every solid cancer.

Angiogenesis :  the  generation of new blood vessels. In  a  human embryo this is critical for the development of limbs and  organs, but  in  adults, new blood vessels do not  normally  grow  except during  reproduction and would healing. Anti-angiogenesis  cancer therapies  are  designed  to inhibit  abnormal  growth  of  blood vessels of tumors, causing them to die.

Anion : a negatively-charged ion.

Antagonist :  a  molecule  that inactivates a  receptor.  This  is usually  accomplished  by sitting on a receptor and  blocking  an activator from binding to it.

Antibody :  a  glycoprotein molecule produced by the  white  blood cells  of the immune system in higher organisms. Its function  is to  recognize  and attach to foreign substances  (e.g.  bacteria, virus),  thereby  marking them out for other  components  of  the immune  system to destroy. There are millions of different  types of antibodies, each designed to bind to a surface feature on  the foreign body (antigen).

Anticodon :  triplet of nucleotide bases (codon) in  transfer  RNA that  pairs with, or is complementary to, a triplet in  messenger RNA. For example, if the codon is UCG, the anticodon is AGC.

Antigen: a substance foreign to the body that induces an antibody reponse. An antigen can be free in solution or occur as part of a cell.

Antigen processing/presenting cell: a type of cell which provokes an immune response from T lymphocytes by binding foreign antigens to their surfaces and then interacting with the T cells.

Antigenic determinant: a molecule (such as a glycoprotein) on the surface of a microbe or macromolecule that triggers an immune response.

Antigenic drift : the accumulation of single amino acid changes over time.

Antigenic shift : when a virus replaces one of its genes with a new one, producing a protein that the immune system has never seen before.

Antigenic switching: the process by which a pathogenic microbesgenetic structure is altered to change its surface antigens in order to avoid being detected by the hosts immune system.

Antigenicity: the ability of a substance to trigger an immune response in a particular organism.

Antisense :  in double-stranded DNA, the strand opposite the  one that is transcribed into mRNA and translated into protein.  Anti-sense  drugs  are  mirror images of small segments  of  DNA  that inhibit the expression of disease-causing proteins.

Antiserum: blood serum containing specific antibodies against an antigen. Antisera are used to confer passive immunity to many diseases.

Apoptosis :  programmed  cell death. Apoptosis  is  a  fundamental biological  process  that is vital to  cell  differentiation  and normal  development.  For example, in human  embryos  it  creates fingers from mitt-like hands. In contrast to necrosis,  apoptosis is  an atraumatic, orderly and predictable self-destruction  that occurs when age or state of cell health dictates. Apoptotic cells shrink  and are rapidly eaten by neighboring cells, before  there is  any leakage of their contents. Deregulation of  apoptosis  is involved  in a broad range of diseases, including  cancer,  heart attack, autoimmune diseases such as lupus, and  neurodegenerative diseases such as Alzheimer's and Parkinson's diseases.

Assay : technique for measuring a biological response.

ATP: adenosine triphosphate (ATP) is a molecule used by the cell to store energy.

Attenuated: weakened. With reference to vaccines, made from pathogenic organisms that have been treated so as to render them avirulent.

Autoimmune  disease:   a  disease  in  which  the  body   produces antibodies against its own tissue.

Autoimmunity: a condition in which the body mounts an immune response against one of its own organs or tissues.

Autosome: a chromosome not involved in sex determination. The diploid human genome consists of 46 chromosomes, 22 pairs of autosomes, and 1 pair of sex chromosomes (the X and Y chromosomes).

Autoimmunity :  a  condition in which the body  mounts  an  immune response against one of its own organs or tissues.

Autonomic  nervous  system : a system that  regulates  the  body's automatic  functions  including  blood pressure  and  heart  rate control, sweating and digestion.

Autophagy: the breakdown and recycling of cellular material within cells.

Autosome : any chromosome other than a sex chromosome.

Autonomic  nervous  system :  a  major  system  of  neurons   that regulates blood pressure, temperature and the body's  circulatory response to stress.

Autophagy :  a  process  in which nucleated cells  are  forced  to gather  food from their own interior to provide the nutrients  to keep its vital functions running. It occurs during starvation and differentiation  in  which cellular components  are  enclosed  by double   membrane  structures  termed  autophagosomes  prior   to degradation  in lysosomes or vacuoles. Autophagy is also  one  of the main ways for a cell to get rid of obsolete parts,  including aged proteins from the cytoplasm and even complete organelles.

Avirulent : unable to cause disease.

Axons :  conduits through which nerve cells  communicate.  Without axon connections, neurons die.

B

BCG :  bacillus Calmette-Guerin, attenuated  tuberculosis  microbe bacillus.  First  tested in the 1970's, today it is  used  as  an adjuvant   and  as  a  treatment  for   bladder   cancer.

B-cells :  lymphocytes formed in the bone marrow that function  in the immune system to produce antibodies.

Bcl family of proteins : intracellular regulators. The Bcl-2  gene encodes  a protein that inhibits apoptosis. High levels of  Bcl-2 promote  cancer  by inhibiting apoptosis.  Fifteen  Bcl-2  family members have been identified in mammals.

Bacillus  subtilis :  a  bacteria  commonly  used  as  a  host  in recombinant DNA that has the ability to secrete proteins.

Bacteria :  single-cell microorganisms without cell  nuclei.  Some help  us to digest food (E.coli) but also cause  many  infectious  diseases.

Bacteria  artificial  chromosome (BAC) : large  segments  of  DNA, 100,000  to  200,000  bases, from  another  species  cloned  into bacteria. Once the foreign DNA has been cloned into the host bacteria, many copies of it can be made.

Bacteriophage  (Phage) :  a  virus that infects  a  bacterium.  It consists  of  a  nucleic  acid  (DNA  or  RNA)  placed  within  a polyhedral capsid composed mainly of glycoproteins. Bacteriophage RNA has been a common cloning vector in genetic engineering.

Bacterium: any of a large group of microscopic organisms with a very simple cell structure. Some manufacture their own food, some live as parasites on other organisms and some live on decaying matter.

Base :  1. A chemical compound that reduces the relative number of hydrogen ions (H+) when dissolved in aqueous solution.  It results in the an increase in the pH of the solution. 2. A nitrogen-containing (nitrogenous) ring molecule that , in combination with a pentose sugar and phosphate group, form a nucleotide, the fundamental unit of nucleic acids (DNA, RNA) and ATP, the energy source of the cell. The nucleotides that  make  up  the  DNA and RNA molecules are  adenine  (A), cytosine (C), guanine (G), thymine (T), and uracil (U). Structurally, cytosine, thymine and uracil are single ring pyramidines, and adenine and guanine are double ring purines.

Base  pair :  the two bases on different strands of  nucleic  acid that bond together.

Base sequence: the order of nucleotide bases in a DNA molecules.

Bioassay : the measurement of the effect of a compound on animals, tissues or organisms in comparison with a standard preparation.

Bioavailability :  the extent to which a drug or  other  substance becomes available to the target tissue after administration.

Biocatalyst: in bioprocessing, an enzyme that activates or speeds up a biochemical reaction.

Biofilm : organized communities of bacterial cells encased in a self-produced slime. The bacteria cells produce signaling molecules, called quorum sensing molecules, that allow the cells to communicate with each other. At a critical cell density, these signals have accumulated and triggered the expression of a specific set of genes, which results in the formation of the biofilm. By growing as a biofilm, bacteria can survive and thrive in hostile environments. Some  60% of bacterial infections involve biofilms, including  P. aeruginosa  in  the lungs of cystic fibrosis patients,  which  is responsible  for  90%  of their deaths.  Other  examples  include catheters, contact lenses, and corroded water pipes. Bacteria not integrated  into or released by biofilm are more  susceptible  to antibiotics.

Bioinformatics :  a new computer-based science to study  molecular dynamics,   including  simulations  of  protein   folding.   Most importantly,  it assigns functions to unknown genes based  on  the degree of homology.

Biological bypass : term for an experimental technique to  produce angiogenesis,  the  creation  of new blood  vessels,  using  gene therapy   or  therapeutic  proteins,  such  as   VEGF   (Vascular Endothelial Growth Factor), to induce migration and proliferation of  endothelial cells, vascular tube formation and connection  to the surrounding vascular network.

Bioreactor: vessel used for bioprocessing.

Biotechnology :  the  use of biological processes to  make  useful products.  More  particularly,  the use of  recombinant  DNA,  or genetic engineering.

Blastema : a structure made up of rapidly dividing immature  cells with the potential to become different tissues.

Blastocyst :  a  hollow  sphere  with  a  15-20  cell  cluster  of embryonic   cells   which  appear  in  the   first   week   after fertilization.  They  migrate  down the fallopian  tubes  to  the uterus.

Blockbuster drug : one with an annual sales exceeding $1  billion. About  25  drugs surpassed that mark in 1998, including  the  top three:  Prilosec  (Astra  AB) for ulcers,  $5.14  billion;  Zocor (Merck),  a  cholesterol  drug, $3.95 billion;  and  Prozac  (Eli Lilly), an antidepressant, $2.81 billion.

Blood-brain  barrier :  a  cellular  barrier  in  the  brain  that prevents the passage of many substance from the circulating blood into  the cerebrospinal fluid, although these substances  readily penetrate most other tissues.

Brachytherapy: a general term for radiation delivered from implants inside the body rather than a machine outside the body (external beam radiation). Silver colored tubes called seeds contain a radioactive element that delivers a uniform and continuous supply of radiation to the tumors.

Buccal delivery : the administration of a drug to the inner cheek.

Burn  rate :  net rate of cash outflow. A common  measure  of  the financial  health  of biotechnology companies that have  not  yet reached  the  break-even point. It is usually  expressed  as  the number of months of burn remaining.

C

cAMP: cyclic AMP nucleotide is a small molecule involved in regulation of certain genes.

CD marker : a type of cell surface marker that varies to  identify the different groups of T-cells.

Cadherins : molecules that bind cells with other cells of the same kinds

Caenorhabditis elegans : the nematode worm. It contains only 1,000 cells  and  is  the  first animal genome  for  which  a  complete physical map has been completed.

Calpains :  a  type of protein-destroying enzyme  found  in  cells throughout  the  body. They switch on when calcium  floods  cells after traumatic brain injury.

Carbohydrate : chain of sugar molecules.

Carcinoembryonic antigen (CEA): an antigen in blood which is elevated in certain cancers of epithelial origin, notably colon, breast, lung and stomach. CEA is a molecule expressed on surfaces of epithelial cells during embryogenesis but is later confined to only the apical surface. Its function is related to cell adhesions. Tumor formation is accompanied with elevated expression of CEA. Blood CEA levels is a tumor marker to detect the recurrence of cancer or residual activity of cancer after surgery. However, CEA is a non-specific marker of ancer, and may be elevated in noncancerous conditions such as cigarette smoking, ulcerative colitis, liver disease, and lung infection. Therefore, CEA is not useful as a screening test.

Carcinoma: cancer that begins in the lining or covering of an organ.

Caspase :  a  family of cysteine proteases, enzymes  that  degrade critical  cellular  proteins. They are involved in  a  number  of biochemical pathways, including inflammation and apoptosis.  They are  normally  in a dormant, or procaspase, state,  and  need  to become  activated  by  cleavage  at  two  aspartic  acids,  which produces  the  large  and small subunits  that  form  the  active enzyme.  The caspases required for apoptosis vary depending  upon the cell type.

Catalysis: the acceleration of chemical reactions. Within the cell, catalysis is generally carried out by proteins called enzymes.

Cation : a positively charged ion.

Cell :  the smallest structural unit of living organisms  that  is able to grow and reproduce independently.

Cell  adhesion molecule (CAM) : protein on the cell  surface  that mediates cell-to-cell binding.

Cell-free extract: the intracellular soup remaining after cells are broken (for instance by grinding) and cell debris is removed by low-speed centrifugation. Cell-free extracts provide a way of studying a biochemical process without having completely purified components.

Cell line : cells that grow and replicate continuously outside the living organism.

Cell-mediated   immunity :  acquired  immunity  in  which  the   T lymphocytes play a predominant role.

Cell  mortality : the ability of cells of normal tissue to  double only  a limited number of times before reaching cell  senescence. This  barrier  to unlimited proliferation is an  important  anti-cancer defense mechanism.

Cellular immunity : second line of immune defense (after  humoral) in  which  T lymphocytes recognize when host  cells  have  become infected  and  destroy them. T lymphocytes, which do  not  secret antibodies, must come close to or make contact with the  infected cell to destroy them.

Centimorgan  (cM) : the distance between DNA markers on a  genetic map.  Named  after American geneticist Thomas  Morgan  Hunt.  Two markers  are  said  to be 1 cM apart if  they  are  separated  by recombination 1% of the time. A cM is approximately a distance of 1 million base pairs.

Central  dogma : the rule of the molecular biology of  the  1950's and  1960's  that held that information flow  in  living  systems always proceeded in one direction: from DNA to RNA to protein. In the  1970's, however, researchers discovered RNA  viruses  called retorviruses which made DNA from RNA.

Centrioles :  the two bundles of short microtubules that form  the core of the centrosome of animal cells.

Centromere: a specialized chromosome region to which splidle fibers attach during cell division.

Centrosome : an organelle located near the nucleus of a cell which is  the  focal point of the part of the cytoskeleton made  up  of microtubules   called  centrioles.  It  replicates  before   cell division,  and then pulls apart the duplicated  chromosomes  into daughter cells. Recent research has associated it with cancer.

Chaperone  molecules :  molecules that help the amino  acids  fold into their one correct shape. Heat shock proteins have been called molecular chaperones because of their functions in guiding newly synthesized proteins to fold and in accompanying proteins to facilitate the assembly of monomer units into active multimers.

Chemokines : proteins that regulate the recruitment and activation of  leukocytes  and  other cells at the  sites  of  inflammation. Chemokines have recently been linked to the pathogenesis of HIV.

Chimera :  an organism that contains the tissues of more than  one genetic   type.   In  genetic  engineering  this   involves   the introduction of a cell or cells into a developing embryo.

Chimeraplasty :  a technique to modify or replace genomic  DNA  by utilizing  a  chimeraplast,  a  DNA-RNA  hybrid  molecule   which activates  the cell's own DNA repair mechanism to carry  out  the required genetic modification.

Chiral chemistry : study of the left- and right-handed versions of molecules. Traditionally, molecules of a particular drug form  in mirror  images,  much  like  left-  and  right-  handed   gloves. Chemically,  they  are identical but the two versions  can  react quite  differently  in the human body. In 1992, the FDA  made  it official  federal  policy that for  pharmaceutical  companies  to market  a drug, they must prove both the efficacy and  safety  of its left- and right-handed versions.

Cis-dominant: refers to a mutation that effects only adjacent genes on the same chromosome (cis from Latin for on this side of).

Cholinergic nerve cells : produce a neurotransmitter that  enables brain cells to communicate.

Chromosome :  the thread-like structures in the nucleus  of  cells containing DNA. Human cells have 23 matched pairs for a total  of 46 chromosomes (22 autosomes plus a pair of sex chromosomes).

Chromosome  inversion : when a chromosome breaks in  two places  and the  intervening chromosome segments reintegrate in  an  opposite orientation.

Chromosomal translocation : when chromosomes break and rejoin  in a  different  way.  About half of all  leukemias  are  caused  by chromosome translocations.

Chronic: of long duration, denoting a disease of slow progress and long continuance.

Circadian  clock :  an endogenous timekeeper that  controls  daily rhythms  in  physiology and behaviour. A feedback loop  works  in sync with environmental light and darkness.

Citric acid cycle : a universal energy producing process in living cells

Clathrin : a protein molecule that transports vital material  from the  membrane  into cells. It has a three-legged  structure  that captures its cargo by folding into a  sphere.

Cleavable  mass  spectometry tags (CMSTs) :  small  molecules,  or tags,  that can be attached by a linker to an oligonucleotide  so that  individual  DNA can be tracked, mapped  and  analyzed.  The linker  can  be  easily  cleaved and  the  tag,  with  its  known molecular weight, can be detected by ordinary mass spectometry.

Clinical  studies :  trials  of drug candidates  that  test  their safety and efficacy to treat a disease.

Clone :  a cell, gene or organism derived from a  single  ancestor cell, gene or organism. It is used to describe a cell carrying  a recombinant DNA fragment.

Cloning: the process of asexually producing a group of cells (clones), all genetically identical, from a single ancestor. In recombinant DNA technology, the use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA is referred to as cloning DNA.

Cloning vector: DNA molecule originating from a virus, a plasmid, or the cell of a higher organism into which another DNA fragment of appropriate size can be integrated without loss of the vectors capacity for self-replication. Vectors introduce foreign DNA into host cells, where it can be reproduced in large quantities. Examples are plasmids, cosmids, and yeast artificial chromosomes. Vectors are often recombinant molecules containing DNA sequences from several sources.

Cochleate :  a  modified  liposome structure; used  as  a  vaccine adjuvant.

Codon :  the triplets of the four DNA bases of which there are  64 combinations.  Most  codons  specify  an  amino  acid   sequence; however, three code for stop signals.

Coenzyme: a substance that enhances or is necessary for the action of enzymes. They are generally smaller than enzymes themselves.

Cohesin : a multi-protein complex that maintains tight  association of sister chromatics. It also binds the centromere.

Cohesion  release :  a  process in  which  sister  chromatids  are separated  from  each other and the mitotic spindle  during  cell division (mitosis).

Colony-stimulating factors (CSFS): a group of lymphokines that induce the amturation and proliferation of white blood cells from the primitive cell types present in bone marrow.

Combinatorial  chemistry : a research technology that takes  basic chemical structures and builds thousands of variations, resulting in large numbers of different but related molecules.

Complement proteins : part of the specific immune system, they are triggered  by  and  form a  complex with  immunoglobulins  and  a foreign particle, which are taken up and destroyed by phagocytes.

Complement system : a group of proteins of the immune system  that is  typically activated during an inflammatory reponse  triggered by a foreign invader.

Complementary  DNA  (cDNA) :  DNA  that  is  synthesized  from   a messenger RNA (mRNA) template. It is used in genetic  engineering to identify and clone the genes that encoded the RNA.

Concentration  gradient : the difference in the  concentration  of ions on either side of a cell membrane.

Congenic  animals : inbred lines of rats used to  examine  several genetic loci that could influence a complex trait.

Conjugation : the direct transfer of DNA from one cell to  another upon direct contact. This transfer depends upon the presence of a plasmid in the donor cell.

Constitutive: when a gene product is produced all the time, rather than in response to induction.

Contig map: a map depicting the relative order of a linked library of small overlapping clones representing a complete chromosomal segment.

Contigs : groups of clones representing overlapping regions of a genome.

Control  group :  the group of patients in a clinical  trial  that receives  current  standard care and/or placebo. Results  of  the control group are compared to results of the treatment group.

Co-repressor: an environmental signal (or efector) that is required to convert a repressor to its active state.

Cortex :  a  thickly  folded 6-layer band  of  brain  tissue  that carries out higher mental capacities in humans and other mammals.

Cosmid : artificially constructed cloning vector containing the cos gene of phage lambda. Cosmids can be packaged in lambda phage particles for infecton into E. coli. This permits cloning of larger DNA fragments (up to 45 kb) than can be introduced into bacterial hosts in plasmid vectors.

Cross licensing: legal, contractual procedure in which two or more firms with competing, similar technologies and possible conflicting claims strike a deal to reduce the need for legal actions to clarify who is to profit from applications of the technology.

Crossing   over :  the  exchange  of  genes  between  two   paired chromosomes.

Cross-resistance :  a  phenomenon in which a  virus's  ability  to resist  the  antiviral  effects of one drug also  enables  it  to resist the effects of others in the same class.

Culture: the cultivation of living organisms in prepared medium.

Culture medium: any nutrient system for the artificial cultivation of bacteria or other cells. Usually a complex mixture of organic and inorganic materials.

Cyto : refers to cell or cell plasm.

Cytochrome  c :  a  protein  that  plays  an  important  role   in generating   energy  within  the  mitochondria  of  cells.   When mitochondria  are  damaged, cytochrome c is  released   into  the cytoplasm,  where  it amplifies a caspase  cascade  of  proteases leading to apoptosis.

Cytodifferentiation : an experimental treatment that uses chemical agents  to  induce  cancer cells to mature and  die  like  normal cells.

Cytogenetics :  the  study of the cell  and  its  heredity-related components, especially chromosomes.

Cytokines :  a diverse group soluble  proteins  and peptides  that  are  primarily involved  in  signaling between cells of the immune  system.  They include  interferons, interleukins, colony stimulating  factors, growth factors, and tumor necrosis factors.

Cytoplasm :  the  contents of a cell contained within  its  plasma membrane,  but  in  the case of  eukaryotic  cells,  outside  the nucleus.

Cytoskeleton :   gel-like  inner  scaffold  underneath  the   cell membrane.  It  is  composed of a continuous  changing  fabric  of proteins  that  allow the cell to change shape  and  motility  in response to changes in the environment.

Cytosol :  the contents of the main compartment of the  cytoplasm, excluding membrane-bound organelles such as endoplasmic reticulum and mitochondria.

Cytotoxic : able to cause cell death.

Cytotoxic T-cells (CTLs) : killer T-cells activated by binding  to specific  epitopes presented by infected cells or other  antigen-presenting cells.

D

DNA :  deoxyribonucleic acid, a nucleic acid that encodes  genetic information.  Its structure was first published in 1953 by  James Watson  and  Francis  Crick,  who won the  Nobel  Prize  for  the discovery. DNA is a double helix molecule composed of a  sequence of four nucleotide bases: A (adenine), G (guanine), C (cytosine), and  T (thymidine) linked via a deoxyribose sugar to a  phosphate molecule. The base pairs form only between A and T and between  G and  C,  thus  the base sequence of each  single  strand  can  be deduced from that of its partner. The bases are spaced along each strand  so that exactly ten pairs occur in the length of  a  full turn  of the helix. The pairs are stacked flat, with 3.4  anstrom units (about one and a third hundred-millionths of an inch) and a tenth  of  a revolution separating a pair from the one  above  or below. The total information content of the human genome consists of about 3 billion bases of DNA sequence divided into the  70,000 to 100,000 segments that represent individual genes.

cDNA :  complementary DNA, sequences of DNA copies of RNA  that  a cell's ribosomes use to express a gene or its protein.

cDNA  library : a collection of DNA sequences generated from  mRNA sequences. It contains only protein-coding (DNA) genes.

mtDNA :  mitochondria DNA. Mitochondria has its own DNA, which  is separate  from  DNA  in  the cells nucleus,  and  appears  to  be inherited exclusively through the maternal line.

DNA hybridization : a technique for joining two strands of DNA  by utilizing  the  affinity of the plus stand of one  gene  remating with  the minus strand of the same gene and never with the  minus strand of another gene.

DNA ligase: a DNA-joining enzyme. During replication, it is responsible for stitching together the DNA segments on the lagging strand into a continuous chain.

DNA methylation : the chemical modification of one of the 4  bases of  DNA. It is used in the normal functioning of cells to  switch genes off and prevent them from expressing proteins that instruct the cell to perform certain functions.

DNA  polymerase :  the  enzyme  that  catalyzes  the  assembly  of deoxynucleotides  into DNA. Shaped roughly like a hand, it  works its  way  along a single strand of DNA, using it as  a  template, chemically  stitching  into place nucleotides to  form  a  second strand of DNA. It also carries out quality control,  proofreading its work and halting production when it detects an error, so that repair enzymes can step in.

DNA  probe : a small piece of nucleic acid that has  been  labeled with a radioactive isotope, dye or enzyme and is used to locate a particular nucleotide sequence or gene on a DNA molecule.

DNA replication: the copying, or duplication, of the genome to make two copies.

DNA sequence: the relative order of base pairs, whether in a fragment of DNA, a gene, a chromosome, or an entire genome.

Data Safety Monitoring Committee (DSMC): an independent, chartered committee that determines the safety of clinical trials. It may also stop a study if it reaches statistically significant efficacy that will not be altered by continuation of the study so placebo patients are not denied access to treatment.

Defensins :  anti-microbial  peptides that are part  of  the  host defense system of eukaryotes.

Dendrimers: synthetic polymers used in many biological applications. They readily enter cells and have little toxicity when given intravenously. They are being developed as delivery vehicles to transport anti-cancer drugs and sensing agents into cells.

Dendritic  cell :  a specialized antigen-presenting  cell  of  the immune  system.  They are believed to arise from  CD34  and  stem cells, which are derived from bone marrow, and are found in every tissue except the brain.

Dielectric barrier : the electric field around an ion which causes it to be repelled from the lipid cell membrane. The cell  employs ion  channels to lower the barrier and provide for the  selective transmembrane ion flow.

Differentiation: the process of biochemical and structural changes by which cells become specialized in form and function.

Differentiation antigen: a biomolecule which can be found by immunoassay (testing for the presence of the biomolecule) only in a particular type of cell in the body. Thus, the biomolecule can serve as a marker for that cell type.

Dimerization :  the  process  of bringing  two  proteins  together within  a  cell. It is the key step in many  cellular  processes, including  gene  activation, protein secretion, cell  growth  and cell death.

Diploid : a full set of genetic material, consisting of paired chromosomes, one chromosome from each parental set. Most animal cells except gametes have a diploid set of chromosomes. The diploid human genome has 46 chromosomes.

Directed  evolution :  a genetic engineering process  in  which  a molecule  is  subjected  to random changes, then  a  molecule  is selected with the desired properties. Also known as DNA shuffling or molecular breeding.

Domain : specialized amino acid sequence of a protein with its own function.  Each   domain  may recognize a  specific  sequence  on another  antigen.  The total combination of domains in  a  single protein determines its overall function.

Double-blinded :  clinical trials in which both the  patients  and the  researchers  do  not know which treatment  each  patient  is receiving. This is used to prevent personal bias from influencing the  reactions of both the physician/researcher and  the  patient and the study results.

Double helix: the shape that two linear strands of DNA assume when bonded together.

Dynein :  protein  molecules that move vesicles  in  the  opposite direction than kinesin.

E

Effector: an environmental signal, positive or negative, that controls the activity of a regulatory protein.

Efficacy: therapeutic activity.

Electron-transfer  proteins :  proteins  in  which  electrons  are released and received. They include about one-third of all  known proteins.

Electron tunneling : the transfer of electrons between  reduction-oxidation (redox) centers within proteins. It requires that redox centers be within 14 angstoms of each other.

Electrophoresis : a technique that uses a weak electric current to cause  molecules  in  a  solution to migrate  across  a  slab  of gelatin, smaller chains moving faster and farther. The result  is a  series  of bands. Gel electrophoresis is sensitive  enough  to discriminate  between small groups of molecules differing  by  as little as one nucleotide.

Electroporation : the creation of reversible small holes in a cell wall or membrane through which foreign DNA can pass. This DNA can then integrate into the cell's genome.

Enantiomer :  a  chirally-pure compound. The isomer of  a  racemic compound,  each  with the same composition but with  a  different arrangement of the atoms resulting in structures that are  mirror images of each other.

Endocytosis :  the uptake of extracellular material into the  cell in   membrane-bound  vesicles.  It  plays  a  role   in   antigen presentation,  nutrient  uptake, clearance  of  apoptotic  cells, pathogen  entry, receptor regulation, hypertension, and  synaptic transmission.

Endonuclease: an enzyme that cleaves its nucleic acid substrate at internal sites in the nucleotide sequence.

Endoplasmic  reticulum (ER) :  an organelle within the cell  where proteins  are  synthesized  by the ribosome and  destined  to  be installed in the plasma membrane as a receptor or to be  secreted outside  the  cell.  It houses  machinery  that  directs  protein folding  and oligomerization. Its products are incorporated  into coat  complex II (COPII) vesicles which bud off from the  ER  are  shipped to the Golgi body.

Endothelium :  the single layer of cells that lines the heart  and blood vessels. Recent research has demonstrated that it  contains molecules  that  can  relax or contract  blood  vessel  walls  or influence  the  function  of  circulating  blood  cells  such  as platelets and monocytes. Nitric oxide, for example, is a gas that is secreted and tells blood vessels to relax and widen,  lowering blood pressure.

Enzymes : protein molecules that catalyze and regulate all aspects of  cell  metabolism.  Each enzyme is  highly  specific  for  the conversion  of  a particular  molecule to a  particular  protein. There are about a thousand different enzymes in most cells,  each capable of catalyzing a unique chemical reaction.

Eosinophils :  white  blood cells of the category known as granulocytes. These cells contain numerous dense granules in their cytoplasm that comprise a battery of highly active digestive chemicals and toxins. Their chief role is thought to be in combating large parasites, although occasionally their activity may be triggered by other agents, potentially leading to damage of normal tissues.

Epithelial cells : a class of cells that forms skin and lines many organs, including the colon, uterus, lungs, and the milk ducts in the breast. Some of them keep growing throughout life; from  them spring the majority of human cancers.

Epitope : the region of an antigen molecule that is unique, therefore responsible for its specificity in an antigen-antibody reaction.

Error catastrophe: a mechanism in which the excessive rate of mutation causes the death of a virus.

Erythrocytes :  red blood cells formed from the division of  other cells in the bone marrow. They contain neither nuclei nor nuclear genes. They live for 100 to 120 days before dying.

Erythropoietin (EPO) : the cytokine produced in the kidney that is essential  for the development of red blood cells  (erythrocytes) in the bone marrow. Amgens recombinant DNA drug, Epogen, for the treatment of anemia, is the most profitable biological agent in the history of the biotechnology industry.

Estrogen; a female sex hormone.

Etiology: causal association of a disease with an agent. The study of the cause of diseases.

Eukaryote :  cells  or organism with  a  discrete,  membrane-bound nucleus. They include all organisms except bacteria, viruses, and blue-green algae.

Excision: the removal of integrated viral, plasmid, or transposon sequences from the host chromosome.

Exogenous DNA: DNA originating outside an organism.

Exon : the protein coding DNA sequences of a gene.

Exonuclease: an enzyme that cleaves nucleotides sequentially from free ends of a linear nucleic acid substrate.

Expressed sequence tags (ESTs) : human gene fragments.

Expression cloning : a technique used to identify and clone a gene by introducing cDNAs into cells and selecting those that  express a particular feature.

F

Fast track designation: under the FDA Modernization Act of 1997, the FDA can designate a product as fast track if it is intended for the treatment of a serious or life-threatening condition, and if it demonstrates the potential to address unmet medical needs for such conditions.

Femtosecond :  the time scale for ultrafast chemical reactions  and internal  motions in molecules. One femtosecond is to one  minute as  one minute is to the age of the universe. Modern lasers  can now routinely produce pulses in this range.

Fetomaternal  tolerance :  the process which prevents  a  mother's immune  system  from attacking her baby, which  contains  foreign genetic material.

Fluorescence-activated  cell sorting (FACS) : a technique for  the rapid, automated separating and sorting of cells in a  population of  cells  that  are identified by their having  been  bound  by distinctive fluorescent chemical tags.

Florescent   In  Situ  Hybridization  (FISH) :  a  technique   for identifying whole or parts of chromosomes using florescent tagged DNA.

Fos related antigens (FRA): a group of phosphoproteins found in the cell nucleus which are structurally similar to the fos oncogenes gene product.

Fractionation: a traditional biochemical approach to understanding a biological process, in which each active component is separated and purified in the test tube.

Free radicals : unstable oxygen molecules associated with  cancer, heart disease, and the effects of aging.

Functional genomics : methods used to study gene function and  the metabolic  pathways in which drugs may interact with proteins  to treat disease.

Fusion :  joining  of the membrane of two cells, thus  creating  a daughter  cell that contains some of the characteristics of  each parent cell. Used in making hybridomas.

G

G  proteins :  a  family  of  proteins  that  are  used  for  many functions,  including vision, taste, smell, control of the  heart and embryonic development. They are one of the largest families of proteins  encoded  in the human genome,  representing  roughly  3 percent of the genome.

GM-CSF :  Granulocyte-Macrophage  Colony  Stimulating  Factor,   a immunologic  cytokine  that  stimulates  the  immune  system   by recruiting antigen-presenting cells, and, later, T-cells.

Gamete: mature male or female reproductive cell (sperm or ovum) with a haploid set of chromosomes (23 for humans).

Gastrulation :  the developmental process that gives rise  to  the three primary tissues from which all organs and cells of the body emerge, including brain cells, pancreas and beating heart.

Gel eletropheresis: a technique used to separate DNA or protein molecules by size. An electrical field is set up across a fel, a jello-like matrix. Small molecules move rapidly through the gel in the electrical field, while larger molecules move more slowly.

Gene :  a sequence of DNA that contains the  chemical  instruction that  direct cells to produce proteins. This process is known  as gene expression. Each gene contains an average of 1,000 to  3,000 paired bases.

Gene expression: the process by which a genes coded information is converted intot he stuructures present and operating in the cell. Expressed genes include those that are transcribed into mRNA but not translated into protein (e.g. transfer and ribosomal RNAs).

Gene  mapping : the determination of the location of a gene  on  a DNA molecule.

Gene product: the biochemical material, wither RNA or protein, resulting from expression of a gene. The amount of gene product is used to measure how active a gene is. Abnormal amounts can be correlated with disease-causing alleles.

Gene splicing : the process of editing out introns from the  first RNA product synthesized, with the remaining exons joined together to form a shortened RNA molecule.

Gene therapy : using genes or segments of DNA as a drug.

Genetic  code: the algorithm that relates codons in genes to  the specific amino acid sequence in proteins.

Genetic engineering: the manipulation of DNA by scientists to create novel genetic combinations. Currently, genetic engineering is widely used in basic research as a means of studying gene function and in medicine to economically generate protein drugs such as human growth factor, interferons, and vaccines.

Genetic mapping: a technique by which the order and relative separation of mutations is inferred from the frequency with which two mutant DNAs exchange segments by genetic recombination to restore a normal gene. The farther two mutations are from each other on the chromosome, the more frequently recombination will occur between them.

Genome : the sum of the DNA normally contained in a cell. Genomic  imprinting: the same gene acting one way if  contributed by the father and another if contributed by the mother.

Genomic library: a collection of clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism.

Genomics : the study of the genetic inheritance of a species.  The methods used to identify and characterize genes.

Genomic  imprinting :  a process by which a gene's  expression  is governed solely by which parent contributed the gene copy,  rather than  by classic laws of Mendelian genetics, in which  genes  are either dominant or recessive.

Genotype : the genetic makeup of an individual or group.

Genotyping : the identification of the particular genetic  pattern in an individual's DNA.

Germ  cell :  sperm  or  ova. A germ cell  has  one  full  set  of chromosomes. At conception, the germ cells of each parent combine to   form  a  single  cell  with  a  full,  dual  complement   of chromosomes.

Glial  cells : cells that help neurons survive and work  properly. They include astocytes, microglia, and oligodendrocytes.

Glucose :  a  sugar  molecule that is the cell's  main  source  of energy.  It stores energy in the form of the chemical bonds  that hold  its various atoms together. If the atoms are  split  apart, the energy is released, which is processed in the mitochondria.

Glycoprotein :  a protein molecule with carbodydrate side  chains. Includes most proteins exposed on the outer surface of the plasma membrane.

Glycosylation :  the  chemical  bonding of  a  sugar  molecule  to another organic compound.

Golgi  apparatus :  an organelle that receives proteins  from  the endoplasmic  reticulum (ER). It is a backup system  for  catching mistakes  that  slip past the ER's quality control  program.  The protein  is  processed  through  six chambers  and  sent  to  its destination.

Granulocyte: one of three types of white blood cell. Granulocytes digest bacteria and other parasites.

Granulocyte-macrophage colony stimulation factor (GM-CSF): a natural hormone that stimulates white blood cell production, particularly that of granulocytes and monocytes (the precursosrs of macrophages).

Growth  factors : proteins that stimulate the  multiplication  and differentiation of various types of immature precursor cells.

Growth hormone: a protein produced by the pituitary gland that is involved in cell growth. Human growth hormone is clincally used to treat dwarfism. Also called somatotropin.

Guanine : a nitrogenous base. It pairs with cytosine (C).

H

HAART : an acronym for highly active antiretroviral therapy.

HLA (Human Leukocyte Antigen ): The Major Histocompatibility Complex in humans. It is located on chromosome VI and consists of a group of highly polymorphic (variable) linked genetic loci that determines the set of glycoproteins found on the surface of all nucleated cells in the body. They are unique to each individual and aid the body in identifying self from non-self. In the autoimmune diseases, this mechanism fails and the body attacks itself. The HLA complex is also important in determining transplant compatability.

HLT testing   : Tests to determines the HLA compatability between potential donors and recipients for organ or bone marrow  transplantation. HLA genes are highly variable, a factor that significantly impacts patients involved in organ and bone marrow transplantation. The goal in transplantation is to accurately match the patterns of HLA variability of the donor and patient to achieve the highest clinical success. DNA-based methods for HLP typing have enabled diagnostic laboratories to better identify appropriate donors.

Half-life : the time required for half of the amount of a drug  to be eliminated from the body through natural processes.

Haploid: a single set of chromosomes (half the full set of genetic material), present in the egg and sperm cells of animals and in the egg and pollen cells of plants. Human geings have 23 chromosomes in their reproductive cells.

Hapten :   the   portion  of  an  antigen  that   determines   its immunological  specificity.  When coupled to a large  protein,  a hapten stimulates the formation of antibodies to the two-molecule complex. Also called antigenic determinant.

Heat shock proteins: the set of proteins produced in response to a heat shock. [See heat shock response.] Many of the heat shock proteins function to refold or to facilitate the degradation of proteins damaged by the heat treatment- a molecular cleanup. Heat shock proteins appear to be critically involved in protein folding and assembly and in the translocation of proteins across membranes under normal conditions as well.

Heat shock response: high temperature is a common environmental stress for all organisms and a potentially dangerous one because the proteins that make cells work are especially sensitive to damage from elevated temperature. All cells react to a heat shock, a sudden increase in temperature, with a coordinated, multigene regulatory response that produces elevated amounts of a class of proteins called the heat shock proteins.

Helix-turn-helix motif: a secondary structure found in many different DNA-binding proteins. In a helix-turn-helix, one alpha-helix is positioned to touch the bases of the DNA binding site and an adjacent alpha-helix lies along the sugar-phosphate backbone. The interaction can be visualized as a thumb and forefinger grip by the protein on a standard DNA double helix.

Hemagglutination: clumping (agglutination) of red blood cells.

Hematologic: having to do with the blood.

Hemaglobin: the red, oxygen-carrying protein found in red blood cells.

Hematopoiesis :  the  formation  of  red  blood  cells,  or   more generally,   of   all   blood   cells,   including   lymphocytes, granulocytes, eosinophils, macrophages, and platelets.

Heteroduplex : in a heteroduplex segment of DNA the two strands come from two different parental DNA molecules. Heteroduplex regions are formed during the process of DNA recombination.

Heterozygosity: the presence of different alleles at one or more loci on homologous chromosomes.

High-throughput screening (HTS) : integrated technologies used  to rapidly  assay  thousands of compounds in  search  of  biological activity  for  drug  discovery.  HTS  assays  are  design  around specific disease targets.

Histocompatibility :  immunologic similarity of tissues such  that grafting can be done without tissue rejection.

Histocompatibility  antigen : an antigen that causes rejection  of grafted  material from an animal different in genotype  from  the host animal.

Histones : proteins in the cell nucleus that provide a core around which  chains of DNA are wrapped. For a gene to be expressed  the DNA chain must be unwrapped from the histone core.

Histone acetyltransferases: molecules that regulate gene expression. They add an acetyl molecule to a tail-like structure on histones which causes a loo

sening of the DAN coils for gene expression.

Histone deactylases: molecules that regulate gene expression. They remove an acetyl molecule from histone tails, causing the DNA to wrap tightly around the histones, which represses gene expression.

HIV-1: the retrovirus that causes the disease AIDS; often referred to simply as HIV.

Holoenzyme: a multi-subunit enzyme with all subunits present (for instance DNA polymerase or RNA polymerase).

Homeobox: a short stretch of nucleotides whose base sequence is virtually identical in all the genes that contain it. It has been found in many organisms from fruit flies to human beings. In the fruit fly, a homeobox appears to determine when particular groups of genes are expressed during development.

Homologies: similarities in DNA or protein sequences between individuals of the same species or among different species.

Homologous chromosomes: a pair of chromosomes containing the same linear gene sequences, each derived from one parent.

Homologous  recombination :  the process whereby  a  foreign  gene replaces the corresponding gene in a cell. Yeast cells were first shown  to have this capacity. Homologous recombination  has  been utilized  in  mice to produce "mouse models" of human  genes  for research.

Horizontal  gene  transfer :  the  process  in  which  genes   are transferred between species via a virus or bacterium rather  than via  gametes  donated  from parents  to  progeny  (vertical  gene transfer).

Hormones :  molecules that carry regulatory signals from one  cell to another.

Human leukocyte-associated antigens (HLA antigens): proteins on the outer part of body cells that help fight illness. These proteins vary from person to person. Scientists think that people with certain types of HLA antigens are more likely to developisulin-dependent diabetes. The HLA antigens are also responsible for histocompatibility reactons.

Humanized   monoclonal  antibodies  (hMAbs) :  antibodies that replace   certain components of a mouse antibody with human antibody components.

Humoral  immunity :  the body's first line of defense in  which  B- lymphocytes  secrete antibodies that recognize and  kill  viruses and  invading  microbes  that are still in the  blood  and  lymph systems before they can invade individual cells in the body.

Hybridization: the process of joining two complementary strands of DNA or one each of DNA and RNA to form  double-stranded molecule.

Hybridoma : a hybrid cell produced by the fusion of an  individual B-cell  with an immortal cell line. It is used in the  production of monoclonal antibodies. It was developed by Cesar Milstein and George Kohler in 1975.

Hydrogen bond: a weak chemical interaction (bond) between different sections of a molecule, created by sharing a hydrogen atom. Hydrogen bonds are responsible for much of the folded structure of proteins and for the base-pairing of DNA.

Hypoalgesia : a decreased perception of pain.

Hypoxia :  a  condition  in  which  tissues  receive  insufficient oxygen.

I

IAP  family  of proteins : inhibitors of apoptosis  proteins  that bind to caspases or procaspases.

Iatrogenic: related to an abnormal state or condition produced in a patient through inadvertent or erroneous treatment.

Idiopathic: denoting a disease of unknown cause.

Immune system: the organs, tissues and cells that provide defenses against invasion by foreign substances, cells and cancer.

Immunoadhesions :  genetically  engineered proteins  that  combine features of antibodies with high-affinity cell surface receptors. Immunex's Enbrel is the first to be approved by the FDA.

Immunoassay :  technique for identifying substances based  on  the use of antibodies.

Immunofluorescence: technique for identifying antigenic material that uses antibody labeled with fluorescent material.pecific binding of the antibody and antigen can be seen under a microscope by applying ultraviolet light rays and noting that visible light that is produced.

Immunogen : any substance that can elicit an immune response.

Immunoglobulins : The five major classes of antibodies: IgA,  IgD, IgE,   IgG,  and  IgM.  Many  quintillions  of   these   Y-shaped antibodies,  with more than a trillion  different  specificities, are found in the body.

Immunology: the study of the immune system.

Immunomodulators :  a  diverse class of proteins  that  boost  the immune  system. Many are cell growth factors that accelerate  the production of specific cells important in an immune response.

Immunoredistribution : an hypothesis that holds that when you  are under  stress  the  total number of immune  cells  in  your  body remains  the  same but are redistributed to where they  are  most useful.

Immunotoxins : specific monoclonal antibodies that have a  protein toxin  molecule  attached. The monoclonal  antibody  is  targeted against a tumor cell and the toxin is designed to kill that  cell when the antibody binds to it.

In situ hybridizaton: use of DNA or RNA probe to detect the presence of the complementary DNA sequence in cloned bacterial or cultured eukaryotic cells.

In vitro: studies or phenomenon which take place outside the body, i.e., in test tubes. From the Latin for in glass.

In vivo: from the Latin for in life and means within a living organism.

Inducer :  a  molecule  or substance that increases  the  rate  of enzyme   synthesis,   usually   blocking  the   action   of   the corresponding repressor.

Initiation codon: the initiation, or start, codon in the mRNA signals the start of the coding sequence for a protein. The initiation codon is usually the triplet sequence AUG, which encodes methionine. The initiator AUG defines the set of mRNA codons used for a given protein; correct initiation is said to define the reading frame of the protein.

Innate immunity: the bodys first line of defense against invading pathogens. It identifies infectious agents by their pattern, or structure, and within minutes mounts a broad, rapid response with macrophages and natural killer cells.

Inositols :  major  signaling  molecules  in  the  cell.  Some  20 different inositols have been discovered with ranging numbers and arrangements of phosphates attached.

Insulitis :  a  process  in which  an  unknown  stimulus  triggers lymphocytes to invade the pancreatic isles of Langerhans to cause type I diabetes.

Integration: the reaction in which viral, plasmid, or transposon DNA is inserted into the host chromosome.

Integrons :  pieces  of DNA containing repetitive  sequences  that allow genes from one organism to be used by another.

Interferons :  a  class  of lymphokine proteins  important  in  the immune response. There are three major types of interferon: alpha (leukocyte),  beta (fibroblast) and gamma  (immune).  Interferons inhibit viral infection and may have anticancer properties.

Interleukins :  a  type  of lymphokine that  regulates  growth  and development  of  white  blood cells.  Twelve  interleukins  (IL-1 through IL-12) have been identified to date.

Interleukin-1  (IL-1)  beta  converting  enzyme :  regulates   the production   of  IL-1  and  gamma   interferon,   proinflammatory cytokines   that  have  been  correlated  with  the   onset   and progression of inflammation.

Interneuron : inhibitory cells that signal other neurons,  usually with short range effect.

Intrathecally : infusion into the spinal fluid.

Intron : non-coding DNA sequence that is transcribed into RNA  but cut  out  before  it is translated into protein.  The  number  of introns  per  gene can range from one to more than fifty.  It  is estimated  that between 75%- 90% of the average gene is  composed to introns. Some scientists have called these introns "junk DNA," although  the preservation of the exact position of some  introns over  billions  of years has made this characterization  open  to question.

Investigational New Drug application (IND): an application to begin studies of a new drug or biologic on humans. The IND gives the plan for the study and contains formulation, manufacturing and animal test result information.

Ion  channels : membrane-spanning proteins that allow  for  rapid, selective  transmembrane  ion flow. This mechanism  underlies  the electrical  signaling  in the nervous system and  other  cellular processes.

Iontopheresis :  the  delivery of drugs across  the  skin  surface under a mild electrical current.

ischemia :  when  an  organ of the body does  not  receive  enough blood.

Isoantigen (alloantigen): an antigen which can cause an immune response n genetically distinct individuals from the same species.

Isotope: one of several possible forms of a chemical element, each differing in their number of neutrons. Both radioactive isotopes and heavy isotopes have been used as a way of labeling molecules of interest in biological experiments, as they differ from the forms found most commonly in nature and can easily be detected.

J

K

K antigen: any of many antigens that are part of a bacterial capsule or form on the outer portion of a cell wall.

Karyotype: a photomicrograph of an individuals chromosomes arranged in a standard format showing the number, size, and shape of each chromosome tyhpe. Used in low-resolution physical mapping to correlate grow chromosomal abnormalities with the characteristics of specific diseases.

Kilobase  (kb) :  unit of length for DNA fragments equal  to  1000 nucleotides.

Kinase : an enzyme that add phosphates to small molecules or other enzymes,  creating signaling molecules or turning enzymes  on  or off.   These  cell  signaling  enzymes   play  a  key   role   in transmitting  signals from the surface of cells (such as  binding of a hormone to a receptor) into the cell's interior and nucleus, thus changing cell behavior and gene expression. Of the  numerous oncogenes identified to date, many appear to be abnormal versions of signalling pathway components, such as protein kinases.

Kinesin :  a protein molecule that transports vesicles  along  the microtubule.

Koch's postulates : Robert Koch, a German microbiologist, proposed three postulates to prove an organism causes a disease: that  the organism occurs in every case of disease; that it is never  found as a harmless parasite associated with another disease; and  that once  the  organism  is  isolated from  the  body  and  grown  in laboratory  culture,  it can be introduced into a  new  host  and produce  the disease again. The discoveries of molecular  biology has  caused most researchers to agree that Koch's postulates  are no longer valid.

L

Laggin strand: in DNA replication, the DNA chain growing in the 5 to 3 direction and elongated continuously from a single RNA primer is called the leading strand.

Leptin :  a hormone made by fat cells that controls  appetite  and metabolism. Recent experiments have shown that leptin may play  a role in angiogenesis.

Leukocytes :  white blood cells, derived ultimately from the  bone marrow, whose main function is to destroy foreign substances such as bacteria, protozoa, and metazoa. The main type of leukocyte is the phagocyte.

Library : a set of cloned DNA fragments.

Ligand :  any molecule that binds to a specific site on a  protein or another molecule.

Linkage: the proximity of two or more markers (e.g. genes, RFLP markers) on a chromosome. The closer together the markers are, the lower the probability that they will be separated during DNA repair or replication processes (binary fission in prokaryotes, mitosis or meiosis in eukaryotes), and hence the greater the probability that they will be inherited together.

Linkage map: a map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together.

Linker: a fragment of DNA with a restriction site that can be used to join DNA strands.

Lipid : organic molecule that is insoluble in water but  dissolves in various organic solvents. Includes fats, oils, and waxes.  The phospholipids form the structural basis of biological membranes.

Lipoproteins: a class of serum proteins that transport lipids and cholesterol in the blood stream. Abnormalities in lipoprotein metabolism have been implicated in certain heart diseases.

Liposome :  closed, semipermeable bilayers of  phospholipids  that can entrap water and solutes. Liposomes have been used to deliver a variety of drugs, vaccines, and DNA (gene transfer).

Locus: the position of a chromosome of a gene or other chromosomal marker. Also, the DNA at that position.

Lumen : the flow surface of arteries.

Lymph: the almost colorless fluid that travels through the lymphatic system and carries cells that help fight infection.

Lymph node: secondary immune organs distributed at discrete locations throughout the body. These organs play a central role in the activation and trafficking of immune lymphocytes in the body.

Lymphocytes :  white blood cells made up of two classes: B-  and  T- cells. Viruses are destroyed mainly by lymphocytes.

Lymphokines :  a class of soluble proteins produced by white  blood cells  that  play  a role, as yet not fully  understood,  in  the immune response.

Lymphoma: form of cancer that affects the lymph tissue.

Lymphotrophic: denoting a virus that tends to bind to and infect one or more subsets of lymphocytes.

Lysophilization :  a process of freeze-drying  proteins,  peptides, viral products, DNA, and antibiotics to permit a shelf stable dosage form.

Lysosomal   storage  diseases :  a  class  of   inherited   enzyme deficiencies   that   results  in  the  accumulation   of   fatty macromolecules  in  the lysosomes of the cell.  Diseases  include Gaucher's, Fabry's, and Tay-Sachs.

Lysosome :  a cell organelle that contains digestive enzymes  that are  released  to  remove intracellular  debris  including  spent organelles and bacteria destroyed by phagocytes.

M

Macrophage : a type of white blood cell produced in blood  vessels and  loose  connective tissues that can ingest dead  tissues  and cells and is involved in producing interleukin-1. When exposed to the  lymphokine "macrophage-activating factor," macrophages  also kill tumor cells.

Macrophage colony stimulating factor (M-CSF): a natural hormone that stimulates the production of white blood cells, particularly monocytes (the precursors of macrophages).

Major histocompatibility complex (MHC) : A group of mammalian genes coding for the glycoprotein cell surface markers that distinguish each cell as self. In humans, the complex is called human leukocyte-associated antigen (HLA).  They vary slightly from  person  to person.  To trigger an immune response against a  virus-  infected cell,  T-  cells  must recognize a viral peptide  along  with  MHC protein. MHC are also involved in the rejection of foreign tissue from  the  body  following a tissue transplant.  This  family  of proteins in also known as human leukocyte antigen (HLA).

Marker: an identifiable physical location on a chromosome (e.g. restriction enzyme cutting site, gene) whose inheritance can be monitored. Markers can be expressed regions of DNA (genes) or some segment of DNA with no known coding function but whose pattern of inheritance can be determined.

Mass  spectrometer : a technique that uses the ratio of  molecular mass to charge to identify various molecules.

Matrix  metalloproteinases  (MMPs) : enzymes  involved  in  tissue growth and wound repair. In tumor metastasis, MMPs are  activated to  degrade type IV collagen, a principal component of the  basal lamina, a specialized form of the extracellular matrix. A  number of MMP inhibitors have entered clinical trials as a treatment for cancer.

Meiosis : a process of cell reproduction whereby the germ cells of the  parents combine and reduce their number of chromosomes to  a single  set  of  23  chromosomes.  This  process  is  not   fully understood.

Memory  cells :  B-  lymphocytes that have been  stimulated  by  an antigen and display the immunoglobulin which matches the antigen. The  next  time  the antigen enters the body,  the  memory  cells divide rapidly to produce a 100-fold higher concentration in  the bloodstream  than the first time around. This mechanism  is  also the way vaccines work against bacterial infection.

Mendel,  Gregor : an Austrian monk whose experiments with peas  in the  mid-19th  century established the laws of  inheritance.  His works  were discovered in the early-20th century  and  influenced the field of genetics.

Mesenchymal  stem cells (MSCs) : the progenitor cells  from  which connective  tissues  (bone,  cartilage,  tendon,  ligament,  bone marrow stroma, fat and muscle) originate.

Meta-analysis :  the critical review and summary of  results  from many  clinical studies and selected characteristics on  the  same subject.

Metabolism: all biochemical activities carried out by an orgnism to maintain life.

Metalochaperones :  proteins that guide and  protect  transitional metal  ions within the cell, delivering them to  the  appropriate protein receptors. They deliver heavy metal ions, such as copper and iron, to enzymes that need them to catalyze vital biochemical reactions, such as cellular respiration, DNA synthesis and antioxident defense.

Metastasis: the spread of a cancer from one part of the body to another. Cells in the second tumor are like those in the original tumor.

Methylation : the addition of a methyl group. In vertebrae DNA,  a process  of  modifying the genetic code by the  additional  of  a methyl  group  (CH3) to certain cytosine  molecules.  Methylation plays an important role in regulating gene function.

Microarray :  slides containing thousands of DNA  molecules  which can  be  tested  for gene  expression,  compound  screening,  and toxicology, yielding hundreds of thousands of data points in  one experiment.  Data- mining techniques called  bioinformatics  then analyze  this  date  into new drug leads  for  biotechnology  and pharmaceutical companies.

Microbiology: the study of living organisms that can be seen ony with the aid of a microscope.

Microinjection: the injection of DNA using a very fine needle into a cell.

Microorganism: any organism that can be seen only with the aid of a microscope. Also called microbe.

Microsatellite DNA: found in all living organisms, DNA that consists of short, apparently functionless stretches of repeating units two to five nucleotides in length. In humans, the most common repeat unit is the dinucleotide, CA. Microsatellites are used as tools for genetic linkage studies to identify genes associated with common human diseases.

Microtubules :  the subcellular scaffolding within  cells.  During cell  division,  they  act as spindle  fibers  to  help  separate duplicated  chromosomes.  Within the cell, they form  tracks  for transporting molecules throughout the cytoplasm.

Mimotypes : peptides that mimic a molecular sequence and produce a specific antibody or immune response.

Missense: missense mutations are mutations that change one amino acid to another in the sequence of a protein, causing the amino acid sequence to have a different meaning, or mis-sense.

Mitochrondrion :  a membrane-bound organelle that  drives  energy, metabolism  and life and death of cells, including apoptosis  and other  key signaling pathways. Mitochondrion has its own  DNA,  a little  chromosome with several genes. Mitochondrial  dysfunction is  a  major contributing factor in Alzheimer's  and  Parkinson's diseases and Type II diabetes.

Mitogen : any substance that causes a cell to divide.

Mitosis : process of cell reproduction whereby the daughter  cells are identical in chromosome number to the parent cells.

Mitotic  spindle :  a complex structure composed  of  microtubules that separates the two sets of chromosomes during cell  division. Cancer  drugs that cause arrest of the cell cycle by  binding  to microtubules    include   paclitaxel,    docetaxel,    etoposide, vinblastine, vincristine, and vinorelbine.

Molten globule : a partially unfolded protein.

Monoclonal  antibody : an antibody produced from hybridoma  clone. It  is  used to produce large amounts of one  specific  antibody, which  may  be  used to identify and isolate  a  specfic  antigen within a mixture.

Monocytes : one of three types of white blood cells produced by the bone marrow. Precursors to macrophages.

Morphological transformation: when cultured cells are infected with a tumor virus such as RSV, the virus can induce a morphological transformation, or cell transformation, causing the cells to have a different shape, and to gain certain characteristics of tumor cells. The viral alternations of the cells represents the cell culture equivalent of malignant transformation to tumor cells in an animal host.

Mutagenesis: the process of treating cells with chemicals, UV light, or X-rays to create mutations in the DNA.

Mutagenic: a treatment that causes mutations. Mutagenic agents include various chemicals, UV light, and X-rays.

Mutation: an alteration in the DNA sequence. Mutations often cause production of altered, or mutant, proteins.

Multigenic: of hereditary characteristics, one that is specified by several genes.

Mutagen: a substance that induces mutations.

Mutagenesis : the production of mutation by agents that damage DNA (e.g. x-rays, ultraviolet light, certain chemicals).

Mutant: a cell that manifests new characteristics due to a change in its DNA.

Mutation :  a  change  in  DNA structure. A  gene  can  mutate  by deletion   or  addition  of  one  or  more  base  pairs,  or   by substitution of one base pair for another. Breaks, crossover, and other recombinant events are also possible.

Myeloma: a type of tumor cell that is used in monoclonal antibody technology to form hybridomas.

Myoglobin: the oxygen-transporting protein of muscle, resembling blood hemoglobin in function.

N

Nanoelectrospray mass spectrometry : a technique which  identifies amino   acid  sequences  by  shattering  protein  fragments   and comparing the mass of the resulting pieces.

Natural  killer  cell  (NK) : a type  of  leukocyte  that  attacks cancerous  or virus-infected cells without previous  exposure  to the antigen. NK activity is stimulated by interferon.

Necrosis :   the   traumatic  destruction  of  cells   caused   by catastrophic damage. It releases degradative products and  active enzymes directly into the surrounding tissue and can cause severe inflammation and extensive damage to those tissues.

Netrins : guidance molecules found on the tip of growth cones that direct  axons to their target during development. They are  found on  or  released  by  neurons and glial  cells  as  well  as  the extracellular matrix (the scaffolding between cells).

Neurons :  cells of the nervous system that carry  information  to and from the brain.

Neurotransmitters: substances produced in neurons that promote or inhibit the conduction of nerve impulses, such as epinephrine, norepinephrine, dopamine, serotonin, and gamma-aminobutyrate.