admin answers:

A) If the haploid DNA content is 2.2 x 10^9 base pairs, then the diploid content is:

2 x 2.2 x 10^9 = 4.4 x 10^9 base pairs and this would be the amount in G1 of the cell cycle.

Since the amount of DNA in G2 is double that of G1, then the amount of DNA in G2 would be:

2 x 4.4 x 10^9 = 8.8 x 10^9

If there are 166 base pairs (that number may be a little high, I think it is closer to 150, but we’ll go with 166 for this problem), then:

8.8 x 10^9 base pairs / (166 base pairs/nucleosome) =
880 x 10^7/166 = 5.3 x 10^7 nucleosomes

b) Even though all the mouse chromosomes are telocentric (centromere is at one end of the chromosome, except for the Y which is acrocentric), there *is* a telomere just beyond the centromere, so each chromatid has two telomeres (one on the centromere end and one on the other end of the chromosome). So, in G2, there would be two chromatids per chromosome and since there are 20 chromosome pairs in the diploid cell, there would be 40 chromosomes at G2, each with two chromatids for a total of 80 chromatids. Since there are two telomeres per chromatid, then there would 160 telomeres at G2.

C) A mouse egg cell is haploid and each chromosome has a single chromatid, so since there are 20 chromosomes in a haploid egg cell, each made of a single chromatid, so there are 20 chromatids in the egg cell. Since each chromatid has two telomeres, there are 40 telomeres in the mouse egg cell.