Prosla^jlandin.— Refers to a group of naturally oc- 
curring, chemically related long-chain fatty acids 
that have certain physiological effects (stimulate 
contraction of uterine and other smooth muscles, 
lower hlood pressure, affect action of certain 
hormones). 
Protein.— .A linear polymer of amino acids; proteins 
are the products of gene e.xpression and are the 
functional and structural components of cells. 
Protoplast.— ,A cell without a wall. 
Protoplast fusion.— A means of achieving genetic 
transformation by joining two protoplasts or join- 
ing a protoplast with any of the components of 
another cell. 
Kecessive gene.— .Any gene whose e.xpression is 
dependent on the absence of a dominant gene. 
Recombinant D\A.— The hybrid DN.A produced 
by joining pieces of DN.A from different sources. 
Restriction enzyme.— An enzyme within a bac- 
terium that recognizes and degrades DN.A from 
foreign organisms, thereby preserving the genet- 
ic integrity of the bacterium. In recombinant 
DNA e.xperiments, restriction enzymes are used 
as tiny biological scissors to cut up foreign DN.A 
before it is recombined with a vector. 
Reverse transcriptase.— .An enzyme that can syn- 
thesize a single strand of DN.A from a messenger 
RNA, the re\ erse of the normal direction of proc- 
essing genetic information within the cell. 
RiN'.A (ribonucleic acid).— In its three forms— mes- 
senger RN.A, transfer RN.A, and ribosomal RNA— 
it assists in translating the genetic message of 
DN.A into the finished protein. 
Somatic cell.— One of the cells composing parts of 
the body (e.g., tissues, organs) other than a germ 
cell. 
'I’issue culture.— .An in vitro method of propagat- 
ing healthy cells from tissues, such as fibroblasts 
from skin. 
Transduction.— The pi'ocess by which foreign 
DNA becomes incorporated into the genetic com- 
plement of the host cell. 
Transformation.— The transfer of genetic infor- 
mation by DNA separated from the cell. 
V'ector.— ,A transmission agent; a DNA vector is a 
self-replicating DNA molecule that transfers a 
piece of DNA from one host to another. 
V'irus.— An infectious agent that requires a host cell 
in order for it to replicate. It is composed of 
either RNA or DNA wrapped in a protein coat. 
Zygote. — A cell formed by the union of two mature 
reproductive cells. 
