Hybrid.— A new variety of plant or animal that re- 
sults from cross-breeding two different existing 
varieties. 
Hydrocarbon.— All organic compounds that are 
composed only of carbon and hydrogen. 
Immunoproteins.— All the proteins that are part 
of the immune system (including antibodies^ in- 
terferon, and cytokines). 
In vitro.— Outside the living organism and in an 
artificial environment. 
In vivo.— Within the living organism. 
Leukocytes.— The white cells of blood. 
Lipids.— Water insoluble biomolecules, such as cel- 
lular fats and oils. 
Lipopolysaccharides.— Complex substances com- 
posed of lipids and polysaccharides. 
Lymphoblastoid.— Referring to malignant white 
blood cells. 
Lymphokines.— The biologically active soluble fac- 
tor produced by white blood cells. 
Maleic anhydride.— An important organic chem- 
ical used in the manufacture of synthetic resins, 
in fungicides, in the dyeing of cotton textiles,, and 
to prevent the oxidation of fats and oils during 
storage and rancidity. 
Messenger RNA.— Ribonucleic acid molecules that 
serve as a guide for protein synthesis. 
Metabolism.— The sum of the physical and chem- 
ical processes involved in the maintenance of life 
and by which energy is made available. 
Mitochondria.— Structures in higher cells that 
serve as the “powerhouse” for the cell, producing 
chemical energy. 
Monoclonal antibodies.— Antibodies derived 
from a single source or clone of cells which 
recognize only one kind of antigen. 
Mutants.— Organisms whose visible properties with 
respect to some trait differ from the norm of the 
population due to mutations in its DNA. 
Mutation. — Any change that alters the sequence of 
bases along tbe DNA, changing the genetic ma- 
terial. 
Myeloma. — A malignant disease in which tumor 
cells of the antibody producing system synthesize 
excessive amounts of specific proteins. 
n-alkanes. — Straight chain hydrocarbons — the 
main constituents of petroleum. 
Nif genes.— The genes for nitrogen fixation present 
in certain bacteria. 
Nucleic acid.— A polymer composed of DNA or 
RNA subunits. 
Nucleotides.— The fundamental units of nucleic 
acids. They consist of one of the four bases— 
adenine, guanine, cytosine, and thymine (uracil 
in the case of RNA)— and its attached sugar-phos- 
phate group. 
Organic compounds.— Chemical compounds 
based on carbon chains or rings, which contain 
hydrogen, and also may contain oxygen, nitro- 
gen, and various other elements. 
Parthenogenesis.— Reproduction in animals with- 
out male fertilization of the egg. 
Pathogen.— A specific causative agent of disease. 
Peptide.— Short chain of amino acids. 
pH.-A measure of the acidity or basicity of a solu- 
tion; on a scale of 0 (acidic) to 14 (basic): for exam- 
ple, lemon juice has a pH of 2.2 (acidic), water has 
a pH of 7.0 (neutral), and a solution of baking 
soda has a pH of 8.5 (basic). 
Phage.— (See bacteriophage.) 
Phenotype.— Tbe visible properties of an organism 
that are produced by the interaction of the geno- 
type and the environment. 
Plasmid.— Hereditary material that is not part of a 
chromosome. Plasmids are circular- and sc'lf-repli- 
cating. Because they ai-e gener ally srirall ;md rela- 
tively simple, they ar-e used in r-ecornbinant DN.A 
experiments as acceptor's of foreign DN.A. 
Plastid.— Any specialized or-gan of the plant cell 
other than the nucleus, such as the chloroplast 
Ploidy.— Describes the number of srUs of chromo- 
somes present in the or-ganism. I'or example, 
humans are diploid, having two hoiirologous sets 
of 23 chromosomes (one set fr-ont each parent) 
for a total of 48 chr'omosomes; manv plants .ire 
haploid, having only one copy of each chro- 
mosome. 
Polymer.— A long-chain nrolecule foiined li'om 
smaller repeating structur-al units. 
Polysaccharide.— A long-chain carbohydrate con- 
taining at least three molecules of sim|)le sug.irs 
linked together; examples would include (ellu 
lose and star'ch. 
Progestogens.— Hormones invoked with ovul.i 
tion. 
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