If a diploid cell has 4 pairs of chromosomes (2n = 8) during G1, how many DNA double helices will be present in G1? in G2? in metaphase? in each daughter cell after cell division is complete?

Let's break down the number of DNA double helices present in each phase of the cell cycle based on the information provided for a diploid cell with 4 pairs of chromosomes (2n = 8):

During G1 phase:

• In G1 phase, a cell is diploid with 4 pairs of chromosomes (2n = 8).
• Since each chromosome consists of a DNA double helix, in G1, there will be 8 DNA double helices, corresponding to the 8 pairs of chromosomes.

During G2 phase:

• Before DNA replication in S phase, the number of chromosomes remains the same (2n = 8).
• However, after DNA replication, each chromosome is composed of two sister chromatids held together by a centromere. So, in G2, the number of DNA double helices doubles.
• Therefore, in G2 phase, there will be 16 DNA double helices, corresponding to the replicated sister chromatids of the 8 pairs of chromosomes.

During metaphase:

• In metaphase, the chromosomes align at the metaphase plate, preparing for cell division.
• The number of DNA double helices remains the same as in G2, which is 16, as the chromosomes are already replicated and consist of two sister chromatids each.

After cell division (in each daughter cell):

• After cell division (mitosis or meiosis), the chromosomes are segregated into daughter cells.
• In each daughter cell, the number of chromosomes returns to the original diploid number of 4 pairs (2n = 8), and each chromosome consists of a single DNA double helix.
• Therefore, in each daughter cell after cell division, there will be 8 DNA double helices, corresponding to the 4 pairs of chromosomes.