Diploid cell during G1 phase

Question

If you measured the DNA content of a diploid cell during the G1 phase (quantity of x amount), what would the DNA content be (in one cell) if measured at metaphase 1 of meiosis 1 was completed? What would the DNA content be at metaphase 2 of meiosis 2? (Please draw a diagram to help in your response).

Answer 1

I take it that X refers to the number of copies of one gene.

A diploid cell during G1 will have 2x of DNA, since it has 2 homologous chromosomes. Each homologous chromosome will contain one copy of a gene. During S phase, the DNA is duplicated (4X). Metaphase 1 is before any DNA has been separated yet, so it will also be 4X here. After anaphase 1, homologous chromosomes are pulled apart putting us back at 2X (We have sister chromatids). Now we enter meiosis 2. DNA is NOT replicated again. So when the DNA lines up for metaphase 2, we will still have 2X DNA (we still have sister chromatids). It is not until anaphase 2 that these are pulled apart, & the resulting cells will be 1x.

During meiosis 1, the cell is diploid, because it has homologous chromosomes. At the end of meiosis 1, the homologous chromosomes are separated & the cell is diploid. The cell still has 2 copies because of the sister chromatids until anaphase 2.

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Kindly,

Michael G.