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Mitosis question?
I have a question regarding the interphase stage of mitosis. The question is At the beginning of interphase in G1, a cell has 16 chromosomes. How many chromosomes would be found in the same cell in G2 of interphase?
My answer was 32 as G2 comes after the S stage stage where DNA is replicated. If the number of chromosome stays the same then what doubles?
Thanks for the help
3 Answers
- Anonymous5 years ago
If you are asked the question: at G1 there are x chromosomes how many will there be at G2, the answer is x, i.e. it is the same. The DNA has doubled but the chromosome number remains the same. How can this be?
At G1 each chromosome contains a single DNA molecule. During S phase each DNA makes a copy of itself by semi-conservative replication. Each of the two DNA molecules at the end of the replication is in a structure called a chromatid. There are two chromatids, which are joined together as a single chromosome.
In your example at G1 there are 16 chromosomes, each containing a DNA molecule. There are no chromatids. So there are 16 chromosomes and 16 DNA molecules. After S phase, in G2, there are 32 molecules of DNA. Each DNA is in one chromatid, therefore, there are 32 chromatids. These are joined in pairs so there are still only 16 chromosomes.
Source(s): Biology teacher - Formerly Peter SLv 75 years ago
The answer = 16. The chromosomes have one DNA molecule each in G1 but in G2 each chromosomes has two DNA molecules ( the DNA has doubled)
