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A diploid cell in G1 has 6 chromosomes. How many chromosomes and how many chromatids are present in each of the following stages?

Here is what I am guessing

  • G1: 6 chromosomes ; 6 chromatids

  • G2: 6 chromosomes ; 12 chromatids

  • Prophase: 6 chromosomes; 12 chromatids

  • Metaphase: 6 chromosomes; 12 chromatids

  • Anaphase: 12 chromosomes; 12 chromatids

  • Telophase: 12 chromosomes; 12 chromatids

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1 Answer 1

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The chromosomes copy at S phase. So S/G2 checkpoint up to early anaphase has 2n. You are on the right track to understanding the cell cycle, important to note the differences between homologous chromosomes (homologous pair) and sister chromatids, while understanding ploidy.

During S (synthesis) phase which occurs between G1 and G2 , all the somatic DNA replicates. So every chromosome gets copied and thus has a sister chromatid.

Animals that undergo sexual reproduction have 2 sets of chromosomes, one from mom the other from dad. The chromosomes of each pair represents homologous chromosomes.

Your answer is almost correct. I believe it could be adjusted to:

G1: 6 chromosomes G2: 6 chromosomes /12 chromatids Prophase: 12 chromatids Metaphase: 12 chromatids Anaphase: 12 separating chromatids Telophase: 12 chromosomes, 6 one each pole of the cell

These very simple figures explain the principles I mentioned earlierhomologous chromosomes

ploidy in sexual reproduction

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