Help with Bio question

Question

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 12 picograms of DNA per nucleus. How many picograms of DNA would be found in a nucleus at the end of G1 and the end of G2?

Answer 1

To answer this question, you want to understand the stages of the cell cycle, which occur in this order:

1. G1 (growth)
2. S (DNA synthesis)
3. G2 (growth and preparation for mitosis)
4. M (mitosis)

The question stem says that there are 12 picograms of DNA found per nucleus immediately after mitosis.

Since a cell continues to grow throughout G1 (no DNA synthesis), there will still be 12 picograms of DNA per nucleus after G1.

During S phase, the cell synthesizes DNA and will basically double the amount of DNA that it has, in preparation for splitting into two daughter cells. After S phase, during G2, the cell continues to grow and double its components in preparation for mitosis. Thus, at the end of G2, there will be 24 picograms of DNA per nucleus.