Meiosis Overview and Key Stages

To produce haploid cells (gametes) for sexual reproduction.

Sexual reproduction increases the genetic diversity of offspring, leading to a higher chance of survival for a species in changing environments.

Sexually reproducing organisms inherit genetic information from both parents, contributing to the unique genetic makeup of each offspring.

Diploid cells have two copies of each chromosome, one from each parent. They are capable of multiplying and differentiating to form a new organism.

Haploid cells, also known as gametes, have only one set of chromosomes. They are specialized for sexual reproduction.

The fusion of two haploid gametes (sperm and egg) creates a diploid cell called a zygote, which develops into a new organism.

Gametes are haploid sex cells produced by sexually reproducing organisms. Examples include sperm in males and eggs in females.

Meiosis is a specialized type of cell division that produces haploid gametes from diploid cells.

Gametogenesis is the process that differentiates gametes, leading to the formation of sperm and egg cells.

Meiosis consists of two distinct cell divisions, Meiosis I and Meiosis II.

After the S phase of interphase, replicated chromosomes are identical copies of each other.

At the end of meiosis, four haploid daughter cells are formed from one diploid parent cell.

The four cells formed at the end of meiosis are haploid, each containing one set of chromosomes.

The four cells formed at the end of meiosis are genetically different from each other due to crossing over and independent assortment.

Prophase I is characterized by the pairing of homologous chromosomes to form tetrads, the occurrence of crossing over at chiasma, and the condensation of chromosomes. The nuclear membrane also breaks down.

In metaphase I, microtubule spindle fibers from the centrosomes attach to the centromeres of each chromosome. The spindle fibers contract, causing the tetrads to align at the center (metaphase plate) of the cell.

Anaphase I involves the separation of homologous chromosomes. Spindle fibers contract, pulling the chromosomes towards opposite poles of the cell, reducing the chromosome number by half.

Telophase I concludes with the decondensation of chromosomes. Nuclear membranes may reform, and cytokinesis occurs concurrently, resulting in two haploid daughter cells.

In prophase II, chromosomes re-condense after a brief interphase. The nuclear membrane breaks down, and centrosomes migrate to opposite poles of the cell.

During metaphase II, microtubule spindle fibers from the centrosomes attach to the centromeres of each chromosome and contract, causing the chromosomes to align at the center of the cell.

In anaphase II, spindle fibers contract, causing the sister chromatids of each chromosome to separate, and move to opposite poles of the cell.

Telophase II involves the decondensation of chromosomes, the formation of nuclear membranes around each set of chromosomes, and cytokinesis, resulting in four genetically unique haploid daughter cells.

Meiosis occurs in specialized cells called germ cells, which are destined to become gametes (sperm or egg cells).