APPENDIX A 
44. PLASMID: A genetic element outside of the chromosome that is 
capable of replicating independently of the chromosome. 
45. POLYMER: A large molecule composed of simpler repeating units. 
DNA is a polymer composed of nucleotides, while starch and 
cellulose are polymers composed of sugars. 
46. PROKARYOTIC ORGANISM or PROKARYOTE: Cells of bacteria 
or blue -green algae which are characterized as being rather small, 
having a single chromosome that is not enclosed by a nuclear 
membrane, and lacking organelles. 
47. RESTRICTION ENDONUCLEASE: An enz 3 nme capable of breaking 
DNA at specific sites. The action of the enz 3 mie is unique in that 
"sticky" ends are formed which can join with other fragments 
of DNA to form a recombinant DNA molecule. In nature, these 
bacterial enzymes restrict invasion of foreign DNA. 
48. REVERSE TRANSCRIPTASE: An enzyme found in certain viruses 
which reverses the normal synthesis of RNA from DNA. DNA is 
formed for the replication of viral RNA. 
49. R PLASMID: A plasmid that carries genetic information for 
resistance to antibiotics and/or other antibacterial drugs. 
50. SHOTGUN EXPERIMENT: An experiment in which all the DNA 
fragments cleaved by a restriction endonuclease are inserted into 
a vector DNA, which is then put into a cell. This is in contrast 
to other recombinant DNA experiments where only selected fragments 
of DNA are inserted into a vector DNA. 
51. STERILIZE: Any act which results in the absence of all life on or 
in an object. 
52. VECTOR: A carrier of a recombinant DNA molecule; usually a 
plasmid or bacteriophage. 
53. VIABLE: Literally, "capable of life. " Generally refers to the 
ability of microbial cells to grow and multiply as evidenced by, 
for example, formation of colonies on an agar culture medium. 
Frequently organisms may be viable under one set of culture 
conditions and not under another, making it extremely important 
to define precisely the conditions used for determining viability. 
54. VIRUS: A submicroscopic agent consisting of a core of nucleic 
acid surrounded by protein, and capable of replicating only in a 
living cell. 
Appendix A — 5 
