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Biology Lab Report Genetic Exchange in Prokaryotes

Biology Lab Report: Genetic Exchange in Prokaryotes

This lab deals with the process of genetic exchange in prokaryotes. There are three main mechanisms of genetic exchange which include transformation, transduction, and conjugation. In transformation, DNA is released from cells in the surrounding environment which is then incorporated into the recipient cells DNA. In transduction, DNA is transferred through a virus to the recipient. In conjugation, genetic exchange occurs through direct contact with another cell and the plasmid is transferred from the donor to recipient. Plasmids are circular modules of double-stranded DNA which are beneficial but not essential. R factors are plasmids which carry genes that confer resistance to antibiotics on the host cell. R factors have been a problem because they are causing many strains of pathogenic bacteria to be highly resistant to antibiotics. Transformation was the first mechanism of bacterial exchange that was discovered. A famous experiment with transformation dealt with injecting mice with an avirulent strain of bacteria with heat-killed cells of a virulent strain killed the mice while injecting these strains separately did not. This established that the surviving cells were recombinant. A genetic exchange of the DNA in the external medium had occurred between the dead cells and the live ones. The bacteria that we are using is E. coli bacteria which are capable of being artificially transformed. They are made competent (capable of being transformed) only after following subjection of cells to calcium chloride solution.

II.Transformation of E. coli

A. Summary – In this lab, we are investigating the method of genetic exchange called transformation through the insertion of plasmid pUCB DNA, which carries the gene for antibiotic resistance to ampicillin, into competent E. coli cells.

B. Procedure – The procedure of this lab is somewhat complicated. 250uL of calcium chloride to 2 separate tubes labeled + and --. Next, transfer a large colony of bacteria from the starter plate to the tube of cold calcium chloride and twirl rapidly. Add 10uL of the plasmid solution to the "+" tube. Then, incubate both tubes on ice for 15 minutes. During this time, obtain 2 Luria agar plates and two Luria agar plates with ampicillin. Label one plate "+" and the other "--". Next, remove the tubes from ice and immediately...

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