AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

MEIOSIS II

• Meiosis II is the second part of the meiotic process.
• The Meiosis II consists of
  • Prophase II
    • Each dyad is composed of a pair of sister chromatids attached by a common centromere.
  • Metaphase II
    • Centromeres are positioned at the equatorial plane.
  • Anaphase II and
    • Centromeres divide and the sister chromatids of each dyad are pulled to opposite poles
  • Telophase II
    • Reveals one member of each pair of homologous chromosome present in each pole. Each chromosome is referred as monad (a combination of maternal and paternal genetic information). Nuclei reform around chromosomes at the poles. Following cytokinesis in telophase II, four haploid gametes result from a single meiotic event.

Functions of Meiosis

1. It helps in maintaining a definite and constant number of chromosomes in a species.
2. Meiosis results in production of gametes with haploid (half) chromosome number. Union of male and female gametes leads to formation of zygote which receives half chromosome number from male gamete and half from the female gamete and thus the original somatic chromosome number is restored.
3. Meiosis facilitates segregation and independent assortment of chromosomes and genes.
4. It provides an opportunity for the exchange of genes through the process of crossing over. Recombination of genes results in generation of variability in a biological population which is important from evolution points of view.
5. In sexually reproducing species, meiosis is essential for the continuity of generation. Because meiosis results in the formation of male and female gametes and union of such gametes leads to the development of zygotes and thereby new individual.