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Question

1. Compare the appearance of chromatin with that of a chromosome in a cell that is ready to undergo cellular reproduction.

2. Why is it essential that a cell's DNA is duplicated before the cell enters mitosis?

3. DNA replication occurs during which phase of the cell cycle? What does a chromosome look like following DNA replication?

4. What happens during the M stage of the cell cycle?

Answer 1

1. Chromatin looks grainy or blobby - no distinct form. Chromosomes have definite threads.
2. DNA has to be copied because mitosis will divide the nuclear material into two daughter nuclei that must have the same amount of DNA as the original cell had. So ... double the DNA, then split it into two stacks.
3. Replication happens during the S stage of interphase. The chromosome is still in the form of chromatin when it's doubled. Chromatin doesn't turn into chromosomes until prophase of mitosis.
4. What's M? The cell cycle has interphase, mitosis, cytokinesis. If M is mitosis, the purpose is to divide the doubled DNA into two identical nuclei.