From simple bacteria to complex man, the blueprint of every living thing
lies within its DNA. The processes of DNA replication and protein synthesis
are complicated yet effective. Nevertheless, these methods are far from
flawless; variations in an organism's genetic code can result from random
mutations. An example of one such aberration is a transposition event, "...in
which genetic elements insert and excise themselves in chromosomal and plasmid
DNA" (Hickman 628).
Human beings and most advanced organisms possess their DNA in chromosome form.
However, many simpler organisms also have plasmids. Plasmids are too small to
hold all of an organism's DNA. They are artificial constructs used to move and
manipulate genes. The plasmid used in this experiment was pDP12. Among the
genes on the pDP12 plasmid is LYS2, a gene found in the yeast Saccharomyces
cerevisae. This gene codes for an enzyme neccesary for the synthesis of
lysine, an vital amino acid. Another gene on the plasmid codes for resistance
to the antibiotic ampicillin.
The well known bacteria, Escherichia coli, served as the vehicle for
this research. Because it reproduces quickly, is easily manipulated, and is
well understood, it serves as an ideal tool for genetic research. A large
single chromosome stores the E. coli genetic code. Our particular
strain of E. Coli, pBR1262, engineered by Dr. Peter Berget, also
contains the Tn5 transposon and a selectable gene that confers resistance to
the antibiotic kanamycin. Normally, E. coli does not contain
transposons. First discovered by Barbara McClintock, transposons (a.k.a.
jumping genes) are responsible for a number of interesting traits, such as the
chaotic pattern on Indian corn. In a transposition event, a gene from one unit
of DNA replicates itself and "jumps" into another unit (chromosome or plasmid)
of DNA. The transposition event we hoped to observe in this experiment was the
movement of the transposon Tn5 gene from the E. coli chromosome into the
LYS2 portion of the pDP12 plasmid.