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Nondisjunction results in an uneven distribution of chromosomes during cell replication. If nondisjunction occurs during meiosis I, the homologous chromosomes do not separate. If nondisjunction happens in meiosis II, sister chromatids do not separate. If a cell has a diploid number of six (2N = 6) before meiosis, how many chromosomes will be in each of the four daughter cells if one pair of chromosomes experiences nondisjunction during meiosis I?

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Correct Answer: B. Two cells will have 4 chromosomes, two cells will have 2 chromosomes.
For an organism with a diploid number of 6 (2N = 6), each of the four meiotic cells will have 3 chromosomes. However, if nondisjunction occurs in meiosis I, one daughter cell will have 4 doubled chromosomes and the other cell will have two doubled chromosomes. One pair of the homologous chromosomes did not separate. However, all chromatids will separate in the second division, resulting in four single chromosomes in two of the products and two single chromosomes in the other two products.
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