In crossing over, the exchange of maternal and paternal chromatids occurs while homologous chromosomes are paired during:
Correct answer: A. Prophase meiosis I
- A. Prophase meiosis I
- B. Prophase meiosis II
- C. Metaphase of meiosis I
- D. Anaphase meiosis II
Explanation
Option A is correct. Crossing over occurs during prophase I of meiosis I, when homologous chromosomes pair up and exchange segments of their genetic material, leading to genetic variation in the offspring. In contrast, Option B is incorrect because prophase II occurs after the homologous chromosomes have been separated, and no crossing over takes place. Option C is also incorrect; during metaphase I, homologous chromosomes align but do not exchange genetic material. Lastly, Option D is incorrect as anaphase II focuses solely on the separation of sister chromatids, with no involvement of crossing over.
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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