chromosomes and chromatids at different mitotic and meotic stages.?

Question

I am easily confused with the number of chromosomes and chromatids at different stages of the mitosis and meiosis. Can someone tell me how many chromosomes are in each stage and how many chromatids are in each and how many are in the female's first polar body and second polar body, and how many are in spermacyte and spermatids and sperm. How many chrmosomes and chromatids are in the wording of tetrads, dyads and monads?

Answer 1

At the beginning of both mitosis and meiosis, there are 46 chromosomes, each duplicated (2 chromatids). In anaphase of mitosis, the sister chromatids are seperated from each other by the spindle, and 46 chromosomes pulled into each daughter cell. In meiosis, the tetrads line up on the metaphase plate in metaphase I. A tetrad is two duplicated homologous chromosomes, so it has 4 chromatids. In anaphase I, the homologous chromosomes are pulled apart (the tetrad is seperated), but the chromosomes themselves are not yet split, so there are 23 chromosomes in each daughter cell at the end of meiosis I. Meiosis II is exactly like mitosis, except with half the number of chromosomes, so when the sister chromatids are seperated in anaphase II, 23 chromosomes are pulled into each daughter cell by the spindle. Meiosis II is when the sister chromatids are seperated.
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