Mice have a diploid number of 2n 40 How many chromosomes wi

Mice have a diploid number of 2n = 40. How many chromosomes will be present in the following cell types? For each, indicate whether the cell is haploid or diploid. primary spermatocyte secondary oocyte first polar body mitotic cell that has just completed cytokinesis How many sister chromatids will be present in these same cell types in mice? primary spermatocyte secondary oocyte first polar body mitotic cell that has just completed cytokinesis

Solution

(a) Primary spermatocytes are diploid (2N) cells, i.e., 40 chromosomes

(b) Secondary oocytes are also diploid (40 chromosomes)

(c) First polar body - haploid (20 chromosomes)

(d) Mitotic cell that has just completed cytokinesis - diploid (40 chromosomes)

Each pair of chromosome has 2 sister chromatids. So,

(e) Primary spermatocyte - 80 sister chromatids

(f) Secondary oocyte - 80 sister chromatids

(g) first polar body - 40 sister chromatids

(h) Mitotic cell that has just completed cytokinesis - 80 sister chromatids