Glossary 
Aerobic.— Growing only in the presence of oxygen. 
Anaerobic.— Growing only in the absence of 
oxygen. 
Alkaloids.— A group of nitrogen-containing organic 
substances found in plants; many are pharmaco- 
logically active— e.g., nicotine, caffeine, and 
cocaine. 
Allele.— Alternate forms of the same gene. For ex- 
ample, the genes responsible for eye color (blue, 
brown, green, etc.) are alleles. 
Amino acids.— The building blocks of proteins. 
There are 20 common amino acids; they are 
joined together in a strictly ordered "string” 
which determines the character of each protein. 
Antibody.— A protein component of the immune 
system in mammals found in the blood. 
Antigen.— A large molecule, usually a protein or 
carbohydrate, which when introduced in the 
body stimulates the production of an antibody 
that will react specifically with the antigen. 
Aromatic chemical.— An organic compound con- 
taining one or more six-membered rings. 
Aromatic polynjer. — Large molecules consisting 
of repeated structural units of aromatic chem- 
icals. 
Artificial insemination. — The manual placement 
of sperm into the uterus or oviduct. 
Bacteriophage (or phage).— A virus that multi- 
plies in bacteria. Bacteriophage lambda is com- 
monly used as a vector in recombinant DNA ex- 
periments. 
Bioassay.— Determination of the relative strength 
of a substance (such as a drug) by comparing its 
effect on a test organism with that of a standard 
preparation. 
Biomass.— Plant and animal material. 
Biome. — A community of living organisms in a ma- 
jor ecological region. 
Biosynthesis. — The production of a chemical com- 
pound by a living organism. 
Biotechnology. — The collection of industrial proc- 
esses that involve the use of biological systems. 
For some of these industries, these processes in- 
volve the use of genetically engineered micro- 
organisms. 
Blastocyst.— An early developmental stage of the 
embryo; the fertilized egg undergoes sex'eral cell 
divisions and forms a hollow ball of cells called 
the blastocyst. 
Callus.— The cluster of plant cells that results from 
tissue culturing a single plant cell. 
Carbohydrates.— The family of organic molecules 
consisting of simple sugars such as glucose and 
sucrose, and sugar chains (polysaccharides) such 
as starch and cellulose. 
Catalyst.— A substance that enables a chemical 
reaction to take place under milder than normal 
conditions (e.g., lower temperatures). Biological 
catalysts are enzymes; nonbiological catalysts in- 
clude metallic complexes. 
Cell fusion.— The fusing together of two or more 
cells to become a single cell. 
Cell lysis.— Disruption of the cell membrane allow- 
ing the breakdown of the cell and exposure of its 
contents to the environment. 
Cellulase.— An enzyme that degrades cellulose to 
glucose. 
Cellulose.— A polysaccharide composed entii eh- of 
several glucose units linked end to end; it consti- 
tutes the major part of cell walls in plants. 
Chimera.- An individual composed of a mixture of 
genetically different cells. 
Chloroplast.- The structure in plant cx'lls w ln're 
photosynthesis occurs. 
Chromosomes. — The thread-like (X)mpon('nt.s of a 
cell that are composed of DNA and protein, I hex 
contain most of the cell’s DNA. 
Clone.— A group of genetically identical cells or- 
organisms asexually descend(Kl fiom a common 
ancestor. All cells in the clone ha\(' the same g»-- 
netic material and ai'e exact cojiies of the original 
Conjugation.— The one-way ti'ansfer of DNA be- 
tween bacteria in cellular contact. 
Crossing-over.— A genetic (;\ent that can occur- 
during celluar replication, which irnoixcs the 
breakage and lounion of DNA molecules 
Cultivar. — An or'ganism dexeloped and perstslcnl 
under cultivation. 
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