Meiosis

The 1st Division

Prophase 1

• During Prophase 1, homologous chromosomes pair up and exchange genetic material through a process called crossing over.

• Chromosomes condense

Metaphase 1

• Homologous chromosome pairs align at the cell's equatorial plane, preparing for separation in the next phase.

Anaphase 1

• Homologous chromosomes separate, with each chromosome being pulled towards opposite poles of the cell, thereby ensuring that each daughter cell will inherit one chromosome from each pair.

• Sister chromatids remain together at this stage, which distinguishes this phase from mitosis, where sister chromatids are separated.

Telophase 1

• One chromosome from each homologous pair reaches each pole and the cell separates into 2 daughter cells through the process of cytokinesis, which signals the end of meiosis I.

The 2nd Division

Prophase II

• Nuclear envelope breaks down, and spindle apparatus forms

• Chromosomes start moving towards equatorial plane

• Chromosomes still have the chromatids attached by the centromere

Metaphase II

• Single chromosomes align on the metaphase plate

Anaphase II

• Centromeres separate

• The 2 chromatids of each chromosome move to opposite poles of the spindle

• The chromatids are now called chromosomes

Telophase II

• A nuclear envelope forms around each set of chromosomes and cytokinesis occurs

• Produces 4 daughter cells, each with a haploid number of chromosomes, leading to genetic variation due to the independent assortment and recombination that occurred during meiosis.

To Increase Genetic Variation

Crossing Over

• Non-sister chromatids from a homologous pair swap sections of chromatid during prophase I, resulting in a different allele combination that contribute to the diversity of the gametes.

Independent Assortment

• Each homologous pair lines up independently during metaphase 1

• Creates a new combination of alleles.

Mutation in DNA Causes

• Smoking

• Exposed to UV or higher frequencies of light