Question

pre - laboratory questions

1. what is a plasmid?
2. what is bacterial conjugation, and what is the significance of plasmids with respect to conjugation?

lab day 1. confirming antibiotic resistance of strain i and strain ii
materials
for each group:
2 sterile inoculating loops
lb plate
lb+str plate
lb+amp plate
lb+str+amp plate
permanent marker
labeling tape
container for bacterial contaminated waste
shared between two groups:
liquid culture of strain i
liquid culture of strain ii
shared (optional):
37°c incubator
procedure

1. on the bottom surface of the petri dish, draw a line down the middle of each of the four different agar plates as shown in figure 2. write \i\ on one side of the line, and \ii\ on the other side.
2. obtain the e. coli strain i and strain ii liquid cultures that will be shared between your group and one other lab group. strain i has a gene for streptomycin resistance (strr) in the chromosome. strain ii has a gene for ampicillin resistance (ampr) on a plasmid (see figure 1).

Explanation:

1. A plasmid is a small, circular, double - stranded DNA molecule that exists independently of the chromosomal DNA in bacteria and some other microorganisms. It can replicate autonomously and often carries genes that confer traits such as antibiotic resistance.
2. Bacterial conjugation is a mechanism of horizontal gene transfer in bacteria where genetic material is transferred from one bacterium to another through direct cell - to - cell contact. Plasmids play a crucial role in conjugation as they can be transferred from a donor bacterium to a recipient bacterium during this process. This allows for the spread of genes, including those for antibiotic resistance, between different bacterial cells.

Answer:

1. A small, circular, double - stranded DNA molecule independent of chromosomal DNA, often carrying useful genes like those for antibiotic resistance.
2. Bacterial conjugation is horizontal gene transfer via cell - to - cell contact. Plasmids are important as they can be transferred during conjugation, spreading genes between bacteria.