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.

40. Based on the figure, for a wild- type S. cerevisiae strain, the total mass of DNA per cell is greatest at a time between the:

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

General knowledge questions.

According to common sense, for wild-type strain, before DNA replication, the number of DNA molecules corresponds to the number of chromosomes; however, after replication, there are two sister chromatids on a chromosome, And there is one DNA molecule on each chromatids, so the number of DNA molecules doubles at this time. Therefore, the number of DNA molecules increases after DNA replication, and the quality of DNA in each cell is also the largest at this time.