Meiosis is a specialized cell division that creates gametes (sex cells), such as sperm and egg cells. The goal of meiosis is to reduce the chromosome number by half, transforming a diploid cell (containing two sets of chromosomes) into haploid cells (with a single set of chromosomes). This halving ensures the correct chromosome number is maintained in offspring after fertilization.
Events of Telophase I
Telophase I is the final stage of the first meiotic division. During this phase, homologous chromosomes, which separated earlier, arrive at opposite poles of the cell. Each pole now contains a haploid set of chromosomes, but each chromosome still consists of two sister chromatids joined at the centromere. These chromosomes may begin to decondense, unwinding to a more relaxed form.
The nuclear envelopes may begin to reform around the chromosome sets at each pole. Simultaneously, cytokinesis occurs, which is the division of the cytoplasm. This process separates the original cell into two daughter cells, each haploid and possessing replicated chromosomes.
Events of Telophase II
Following Telophase I and a brief interkinesis (a resting phase without DNA replication), cells enter Meiosis II. In this stage, the sister chromatids, which were still attached after Meiosis I, separate and move to opposite poles of each of the two cells. These separated sister chromatids are now considered individual, unreplicated chromosomes.
As the chromosomes reach their poles, nuclear envelopes reform around each set of chromosomes. The chromosomes then decondense. Concurrently, cytokinesis occurs in both cells, dividing their cytoplasm. This results in the formation of four genetically distinct daughter cells from the original parent cell.
Final Products of Meiotic Telophase
Meiosis, concluding with Telophase II and cytokinesis, yields four haploid daughter cells. Each of these cells contains half the number of chromosomes of the original parent cell, and these chromosomes are now unreplicated. For humans, these haploid cells are the gametes: sperm in males and egg cells in females.
These gametes are not genetically identical to each other or to the parent cell. This genetic variability arises from events such as crossing over and independent assortment that occur in earlier stages of meiosis. The reduction in chromosome number and the generation of genetic diversity are vital for sexual reproduction and species adaptation.