Question

Meiosis is an important source of genetic variation in sexually reproducing organisms. Identify the events in meiosis that result in segregation and independent assortment and how these two mechanisms produce genetic variation in the next generation. Use the following terms in your response: genes; alleles; homologous chromosomes; non-homologous chromosomes.

Answer 1

1. A diploid parent has two pairs of homologous chromosomes and each parent contributes one pair of chromosome to the child cell in first part of meiosis.
2. Homologous chromosomes of each pair cross-over or exchange their chromatids (carrying genetic information), in Meiosis I.
3. As a result of cross-over, two homologous chromosomes get genetic information of another chromosome appended on one of the chromatid. It gives rise to two daughter nuclei, each having a pair of Non homologous chromosomes.
4. These two daughter nuclei, again divide into two parts producing 4 haploid nuclei in Meiosis II. Each haploid nulei has a single pair of Non homologous chromosome.

Importance of Segregation: New combination of DNA that is created during cross-over is very important in producing genetic variation in the next generation. It produces new alleles, which can be useful for particular species. Segregation occurs in both events of Meiosis I and II, in prophase. In Meiosis II, it involves separation of sister chromatids.

Importance of Independent Assortment: In metaphase I, all the chromosome pairs allign at the equatorial line, in a proper way to go independently towards poles in anaphase. This process also contributes in the formation of daughter nuclei with one pair of chromosomes each , at the end of meiosis. Recombination of genetic material in DNA produces genetic variations.