Two phenotypes are found for the cuteness trait, cute (C) which is dominant to e

Question

Two phenotypes are found for the cuteness trait, cute (C) which is dominant to extreme cute (c). You have a cute Stevious whose mother was extreme cute. Determine the number of copies of the cute allele present in each stage of meiosis.

I know the genotype for the Stevious is Cc.

anaphase of mitosis - 2 copies
anaphase 1 of meiosis - 2 copies
anaphase 2 of meiosis - 0, 1, or 2
prophase of mitosis - 2 copies
prophase 1 of meiosis - 2 copies

I was just wondering if someone could tell me why in anaphase 2, there could be 0, 1 or 2 copies of the allele. And could someone give me the number of copies at each stage so I can reason it out?

Explanation / Answer

The genotype of the Stevious is Cc. In prophase of mitosis there are 2 copies of the genome. This replication is necessary for the synthesis of two daugther cells with the same genotype as the parent cell. In anaphase of mitosis, the segregation of sister chromatids occurs but the cell does not divide. Hence there are 2 copies of the genome. In prophase I of meiosis, DNA replication occurs.  Hence there are 2 copies of the genome. In anaphase I of meiosis, segregation of homologs occurs but the cell does not divide. Hence, there are 2 copies of the genome. In anaphase II of meiosis, segregation of sister chromatids occurs as in anaphase of mitosis. But the difference is that the chromosome number is halved and separation into daughter cells occurs. Hence, the daughter cells can have 2 alleles or 1 copy of the genome.

A cell can have 0 copies of the genome in case of non-disjunction where the chromosomes divide unequally between the two cells. One cell can then get two alleles and the other will get 0 alleles.

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