Brewer’s yeast formally known as Saccharomyces cervisiae is an organism used in many genetic studies and techniques. This single cellular organism is used to show basic biological processes in a simpler form s scientist can study certain biosynthetic pathways. The experiment to be performed uses the knowledge of mutagenesis of yeast to study how changes may occur in size, morphology and or color in the white yeast cells using UV lights. With this knowledge of mutagenesis of yeast the adenine biosynthetic pathway can be derived from said experiment. With the use of different nutritional mediums/levels (minimal, minimal+adenine, YPD), the biosynthetic pathway can be seen clearly. The hypothesis states that the gene alteration in ADE1 or ADE2 generates red mutant strains. After prolonged exposure to UV lights, it resulted in decreased viability of the healthy cells. The use of different nutritional mediums proved that white strains grew on each plate and is able to synthesize its own adenine. No red yeast grew on the medium, red yeast growth is dependent on a medium without adenine. Red yeast cells were isolated and amplified both the strains were sequenced and compared. The hypothesis was proved; there was a mutation present in ADE2 gene. This mutation caused the red pigmentation of the HB2 strain. It was visible that on bp 800 where there was cytosine it was changed to thymine which was present in the red strain, instead of coding for leucine it coded proline.
Yeast is a microrganism that has been used for centuries by scientist to development products used by man, including cheese wine and cheese via the use of fermentation. Because of the simplicity of the yeast cells, understanding the mechanism which interacts with genes and it products for the gene it expresses for can be seen. Saccromyces cervisiae, can be studied by manipulating the genes and creating new innovate ways to figure out various diseases, genetic manipulations, genetic mutations and heredity given that the yeast has a short life span and large progeny are easily attainable. Yeast genetic imposes importance since the metabolic nature of yeast cells is similar to that of humans.
From white yeast cells, red yeast has been seen. Mutations can occur when the gene has loss of enzymatic activity from loss of function ability of the white strain that changed to the red phenotype. In normal wild type, yeast is able to synthesize its own adenine, in mutations; they may not perform this task because of the loss enzymatic activity which disallows the biosynthetic pathway. The hypothesis of this experiment states that the red strain mutations arises from the ADE1 and ADE2 gene in the adenine biosynthetic pathway in the white yeast strain. This is due to blockage of the several crucial steps in the adenine biosynthetic pathway, changing the white phenotype to the red phenotype.
Materials and Materials
UV mutagenesis * 8 YPD plated were obtained, these were nutrient rich medium. A Bunsen burner was used to sterilize the tools used to aliquot 100μl of HAO liquid medium of yeast cells on 6 plates. With the use of a sterile spreader the yeast culture uniformly on the plate. * At different time intervals, 5 plates were exposed to UV lights. The plates used as negative control was labeled 0. Each plates was exposed at 10, 20, 20, 40 and 80 seconds respectively * The 7th plate is used as another control plate since the first plate will have too many colonies to count. A 1:10 dilution was made by pipeting 100µl f the original culture into 900µl of sterile water using proper sterilization techniques. The mixture was inverted a couple of times to ensure the contents of the test tubes were properly mixed. This was the spread (100µl) on the 7th plate. This was done to achieve to a lowered cell count. * All 7 YPD plates were face down and were properly placed in the incubator at 30⁰C * The final YPD was used for practice runs to learn