You are studying a mutant in S. cerevisiae that you have named spo31, and you ha

Question

You are studying a mutant in S. cerevisiae that you have named spo31, and you have made a deletion allele. spo31A mutants have no apparent defects in mitosis. However, when you sporulate spo314 cells, they form inviable spores. To learn more about the role of spo31 in meiosis, you do a homozygous GFP dot experiment TetO repeats are integrated close to the centromere of chromosome V and tetR-GFP is co- expressed. You transfer wild-type and spo31 mutant diploid yeast cells to sporulation medium and take samples of the culture every hour for ten hours, which is enough time for yeast cells to undergo meiosis. You stain DNA with DAPI and look at your samples by fluorescence microscopy. You count 100 binucleates and tetranucleates, which indicate that anaphase l and anaphase ll have occurred, respectively You get the following results Wild-type 05% 99.5% 05% 995 Spo31 49% 51% 48% 62% A. Is the spo314 mutant undergoing a nondisjunction event? If so, is it a meiosis l or meiosis lII nondisjunction? Explain in one sentence. (4 points) B. You notice that binucleate cells accumulate earlier during your timecourse in your spo31A strain compared to wild-type. Given this information and the GFP dot data, propose an event in meiosis in which SPO31 functions. (4 points)

Explanation / Answer

From the result, the spo31 is highly associating with nondisjunciton. This is because we are getting almost equal percentage of spo31 expression. The spo31 mutants are healthy and do not show any irregularities but when they reproduce they produce nonviable cells because of homozygous recessive genotypes in dead offspring.

The non disjunction occurred in meiosis I because meiosis II perform only doubling of their genome without disjunction.

Part B- this mutation may affect the acetylation or methylation of chromatins. Demethylation is important in segregation of the homologous chromosomes. Therefore, spo31 mutation may relate with this.

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