Question

A mature rat sperm cell has 2.5 µg of genomic DNA that is equivalent of a haploid genome. Compared to this sperm cell, the amount of genomic DNA (in µg) in a somatic cell, which is in the G2 phase of cell cycle, will be _______ (in integer).

Hint:

Remember: Haploid gamete = 1n DNA. Somatic G1 = 2n. After replication (G2) = 4n. So, compare directly using multiples of the haploid DNA amount.

Answer 1

Step 1: Haploid vs diploid DNA content. Sperm = haploid (1n) = 2.5 µg DNA. Somatic cell (diploid, 2n, G1 phase) = 2 × 2.5 = 5 µg DNA. Step 2: DNA content in G2 phase. During G2, DNA has already been replicated (before mitosis), so the DNA content is 4n. Thus, DNA content = 4 × 2.5 = 10 µg.