Saccharomyces cerevisiae is a diploid yeast species that can reproduce either sexually or asexually. An experiment was performed
to induce mitotically dividing S. cerevisiae cells in G2 to undergo meiosis. Which of the following best describes the steps these cells will follow to form gametes? A. The first division will result in crossing over between homologous chromosomes, and the second division will reduce the original number of chromosomes by half in the daughter cells.
B. The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will result in each daughter cell having one-fourth of the original number of chromosomes.
C. The first division will move single chromatids to each daughter cell, and the second division will double the number of chromosomes in each daughter cell.
D. The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.
D. The first division will reduce the number of chromosomes by half for each daughter cell, and the second division will move single chromatids to each daughter cell.
Explanation:
Gametes are formed by meiosis in diploid gamete mother cells. During gamete formation, the gamete mother cell in the yeast would undergo meiosis I. During first division (meiosis-I), the process of crossing over during prophase-I creates genetic variations and movement of homologous chromosomes to the opposite poles during anaphase-I reduces the chromosome number to half in each daughter cell.
Two daughter cells are formed by the end of meiosis-I each of which enters meiosis-II. Splitting of centromere and separation of sister chromatids during anaphase-II of meiosis-II results in the movement of single chromatids to the opposite poles of the cells.
