For a hypothetical organism a typical diploid cell in G1 has

For a hypothetical organism, a typical diploid cell in G1 has 10 chromosomes, including a total amount of 1.2 Gb DNA.

a. How much DNA is in a cell in the G2 phase, right before mitosis? ____
b. How many chromosomes are present in this G2 cell, right before mitosis? ____ c. How many chromosomes are present during metaphase? ____
d. How many chromosomes are present during anaphase? ____
e. How many pairs of homologues are found in this organism? ____

Solution

Answers:

(a) 2.4 Gb of DNA.

The amount of DNA gets duplicated during S phase. Thus, G2 phase also contains 2.4 Gb DNA since the cell has not yet entered mitosis.

(b) 10 chromosomes.

The cell in the G2 stage contains 10 chromosomes but with double number of chromatids.

(c) 10 chromosomes.

During metaphase, the cell contains 10 chromosomes with double the number of chromatids which still remain attached at the centromere.

(d) 20 chromosomes in total. The 10 chromosomes with double the number of chromatids during metaphase gets separated at the centromere during anaphase to give rise to two separate chromosomes for each.

(e) 5 pairs.

The organism has 10 chromosomes in the diploid cell. So, there are 5 pairs of homologous chromosomes present i nthe cell.