Question

An ovum of an animal has 2.5 pg of DNA in its nucleus. The amount of DNA at the end of G${}_2$ phase will be

• A. 2.5 pg
• B. 5 pg
• C. 250 pg
• D. 10 pg

Answer 1

The correct option is D 10 pg

• An ovum is a haploid cell. It is having half the DNA content. It will fuse with sperm. The sperm is also a haploid cell having half the DNA content. When sperm fuses with the egg to form a zygote, the DNA content is restored to that in a normal diploid cell.
• Thus, if the ovum contained 2.5 picograms the zygote will contain 5.0 picograms of DNA. Now, this zygote shall pass through the first growth phase or G${}_1$ phase and then synthesis or S phase.
• In the S phase, DNA will undergo replication and consequently DNA content will become double or 10.0 picograms.
  

So, the correct answer is option D.