Passage VI

In the yeast Saccharomyces cerevisiae, the function of meiosis is to divide a diploid cell into 4 haploid cells called spores. During meiosis, the 2 copies of a chromosome, or homologs, undergo DNA replication (when each homolog becomes a linked pair of sister chromatids) followed by 2 rounds of chromosome segregation (separation into different cells) called Meiosis I and Meiosis II. The figure shows the homologs of a particular chromosome during meiosis in a wild-type S. cerevisiae strain and also in 2 mutant S. cerevisiae strains (Mutant A and Mutant B) each having a different mutation that affects meiosis.

37. Suppose that 10 chromosomes were found in each of the spores of another species of yeast, Species X. Assuming that there were no mutations that affected the formation of the spores, what is the diploid number of chromosomes of Species X ?

Answer and Explanation

Your Answer is

Correct Answer is C

Explanation

According to the no mutations mentioned in the question stem, it can be judged that the corresponding is wild-type strain; it can be seen from the figure that the cells before meiosis have 2 chromosomes, and after Meiosis II, the wild-type strain produces There will be 1 chromosome in each spore, which is the process from diploid to haploid, and the number of chromosomes in each cell is halved. So if there are 10 chromosomes in the haploid spore, there are 20 chromosomes in the original diploid cell