John Domanick - Lab Report 1

John Domanick - Lab Report 1 - Effect of Cologne on lacZ-...

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Effect of Cologne on lacZ - Gene Reversion Rate in Escherichia coli as Determined by Modified Ames Test By John Domanick and Akash Vadalia
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ABSTRACT Effect of cologne on lacZ - reversion rate in E. coli J. Domanick and A. Vadalia, Department of Biology, Brandeis University Scientists have shown that there are many factors that effect DNA mutation rates. One such factor is the introduction of chemicals into cells, which can increase the rate of mutation in said cells DNA if these chemicals are mutagenic. I investigated the effect of introducing cologne into Escherichia coli (E. coli) cells on the mutation rate of the E. coli DNA. The cologne used contains denatured alcohol, which is known to be toxic. To observe the mutagenicity of the cologne I focused on mutations affecting the defective lacZ gene. Two strains of E. coli colonies were grown in three different environments; a lacZ - strain, and a lacZ - /MutS - strain were grown on plates of solely lysogeny broth (LB) media, and plates of LB/IPTG/Xgal media, both with and without the presence of cologne. LB plates were used to obtain a viable count of the E. coli colonies. LB/IPTG/Xgal indicator plates were used to determine both the reversion rate of mutant lacZ - E. coli to prototrophic lacZ + E. coli , and the mutagenic frequency of cologne, by causing any revertant colonies to exhibit a blue color for easy recognition. The lacZ - strain was found to have a one hundred percent (100%) reversion rate, while the lacZ - /MutS- strain was found to have a zero percent (0%) reversion rate. The mutagenic frequencies were also found to be the same as the reversion rates, 100% for lacZ - cells and 0% for lacZ - /MutS - cells, which suggests that the cologne used is not a mutagen, but further studies are needed to be sure of this. Further studies can be performed to assess whether the cologne may be causing mutations that cannot be observed in this experiment, due to mutations in other genes, or non-point mutations in the lacZ - gene. One such study could include the amplification of E. coli DNA before and after the addition of cologne, through a polymerase chain reaction (PCR), and then subjecting the DNA to restriction enzyme digestion and gel electrophoresis to observe any mutations throughout the entire genome.
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INTRODUCTION In 1971 Dr. Bruce Ames developed a test called the Ames test, which is used to determine the mutagenicity of a tested chemical in bacterial cells. The mutagenicity of a chemical is the property of the chemical to cause changes in a cells DNA. Ames went on to test over 300 chemicals to show that the introduction of extraneous chemicals into a cell can indeed mutate the DNA of said cell (Reifferscheid et al. 1991). The DNA and replication systems for DNA in bacteria are the same molecules and
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This note was uploaded on 10/06/2011 for the course BIOL 18 taught by Professor Kc during the Fall '10 term at Brandeis.

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John Domanick - Lab Report 1 - Effect of Cologne on lacZ-...

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