Biological mutations play an integral role in the long-term survival of populations due to the potential benefit that the genetic variance provides. The main objective in this laboratory was to utilize the replica-plating technique to determine whether copper-tolerant mutants in Saccharomyces cervisiae arise spontaneously or if they are induced by their environment. This type of baker's yeast is ideal for mutation experiments due to the specimens quick reproduction ability. Following several serial dilutions, individual yeast colonies were able to be produced on a agar medium. Through the technique of replica-plating, cells from these colonies were able to be transferred to three separate petri plates in the same spatial arrangement they were found on the original plate. One of these plates was prepared with a standard agar medium, while the other two contained a copper-based agar. The cultures were consequently refrigerated in order to prevent growth after the yeast reached 3 mm in diameter. The results of the experiment showed that the location of the mutant colonies were generally identical on all three petri plates. These findings s

Some of the data obtained in this experiment contradicted the expected results. There should have been approximately ten preexisting mutants on each of the replica plates. However, 24 colonies were found in identical locations on their respective plates. A possible explanation for this occurrence may be traced to the agar medium itself. If the copper based agar medium was not concentrated enough, a significant number of cells may still be able to reproduce and grow. As a result, similar colonies may be regarded as possessing the genetic variation. This can account for the high number of individual colonies. However, most of the results that were obtained in this experiment coincided with the expected results.

Based on the results of the experiment, mutations are pre-existing and occur spontaneously in the environment. In the experiment, three plates were prepared utilizing two different types of growth medium. The first plate consisted solely of a standard agar medium. This plate served as the control due to the fact that the experiment called for its comparison to the two copper-based plates. Furthermore, the first plate exemplified the non-selective medium, whereas the copper containing agar plates served as the selective medium.

X2 = å (O-E)2 O= Observed number in class

Their colonies would be located on different parts of the replica plates. Following the results, a chi-square analysis can be performed to assess the goodness of a fit between a set of observed numbers and the theoretically expected numbers. (Hartl, Jones; p. 109)

Some common words found in the essay are:
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