When does a human cell normally contain 92 chromosomes?

Answer 1

Human cells NEVER normally contain 92 chromosomes. A diploid human cell prior to replicating its DNA has 23 pairs of non-replicated chromosomes (46 total). A diploid human cell after replicating its DNA has 23 pairs of replicated chromosomes (46 total). The difference is that each replicated chromosome consists of two DNA molecules called 'sister chromatids'. Non-replicated chromosomes consist of only one DNA molecule (it is not called a chromatid because chromatids are like twins--if you only have one you don't say there is one twin. Thus, you can say that a human cell following DNA replication has 92 chromatids, but never 92 chromosomes.

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Actually, there is a certain period in Mitosis of the cell cycle where you will temporarily have 92 chromosomes - during Anaphase and Telophase ( Mitosis consists of 4 phases occurring in the following order: Prophase, Metaphase, Anaphase, Telophase).

As explained above, 46 sister chromatids are produced after DNA replication (which occurs in synthesis phase of the cell cycle). During Anaphase, the 46 sister chromatids separate, resulting in 92 chromosomes, or 2 sets of 46 chromosomes. Each set then travels to opposite ends of the cell. Next, during Telophase, the cell then elongates and the nuclear envelope forms around each set to form two nuclei.

Then next in Cytokinesis, the cell actually slits into two cells, each with one nucleus holding 46 chromosomes.