Definition of Meiosis
Meiosis refers to a specialized type of cell division that occurs in sexually reproducing organisms. It involves the division of a diploid cell, which possesses two sets of chromosomes, into four haploid cells, each containing only one set of chromosomes.
Stages of Meiosis
Meiosis consists of two consecutive divisions, known as meiosis I and meiosis II. Each division is further divided into distinct stages:
Meiosis I:
- Prophase I: Chromosomes condense, homologous chromosomes pair up, and crossing over occurs.
- Metaphase I: Pairs of homologous chromosomes align along the cell’s equator.
- Anaphase I: Homologous chromosomes separate and move to opposite poles of the cell.
- Telophase I: Chromosomes reach the poles, nuclear envelopes may reform, and the cell begins to divide.
Meiosis II:
- Prophase II: Chromosomes recondense if necessary, and new spindle fibers form.
- Metaphase II: Individual chromosomes align along the equator of each cell.
- Anaphase II: Sister chromatids separate and move towards opposite poles.
- Telophase II: Chromosomes arrive at the poles, nuclear envelopes reform, and the final division of the cell occurs.
Role of Meiosis
Meiosis plays a crucial role in sexual reproduction by producing gametes (sperm and eggs) with half the number of chromosomes found in somatic cells. These haploid gametes combine during fertilization to restore the diploid chromosome number in offspring, creating genetic diversity.