Question

Does the number of chromosomes remain the same as produced by meiosis I?

Answer 1

Meiosis is a division that occurs in diploid cells and gives rise to four haploid cells or nuclei, each having half the number of chromosomes as compared to the parent cell. The division was first studied by Benedict (1887), Strasburger (1888), Sutton (1900), Winiwarter (1900) in different organisms. Farmer and Moore (1905) introduced the term ‘meiosis’ for the first time.

Complete answer:
The interphase of meiosis is similar to the interphase of mitosis except that the S-phase is prolonged. A distinct G2 phase is either short or altogether absent. The meiosis division takes place just after DNA and chromosome replication is completed.

Meiosis involves two successive nuclear divisions, which occur one after the other. Meiosis I and meiosis II are two divisions.
i) During meiosis I, the chromosomes become genetically different due to crossing over and their number is reduced to half. Therefore, meiosis I is also called heterotypic and reduction division.
ii) During meiosis II, the sister chromatids of each chromosome are separated and go to separate daughter cells. Then, the chromosome number remains the same as produced after the end of the first division. Therefore, meiosis II is also called homotypic or equational division.

Note:
- Meiosis I separates the homologous chromosomes to reduce the chromosome number to the haploid stage. It is essential for sexual reproduction. By forming a new combination of genes and a random assortment of paternal and maternal chromosomes it introduces variation.
- Meiosis II helps to separate univalent chromosome chromatids which become dissimilar due to crossing over.