Meiosis

Meiosis

A type of cell division that reduces the chromosome number by half, creating four haploid cells from a diploid parent cell.

Haploid

A cell or nucleus having a single set of unpaired chromosomes, one copy of every chromosome.

Gametes

Reproductive cells (sperm and egg) that are haploid and combine during fertilization.

Diploid

A cell or nucleus containing two complete sets of chromosomes, one from each parent.

Homologous Chromosomes

Chromosomes that have the same structural features and genes, although the alleles may differ.

Tetrad/Bivalent

A pair of homologous chromosomes physically held together, consisting of four sister chromatids.

Crossing Over

The process where non-sister chromatids exchange genetic material, contributing to genetic variation.

Prophase I

The first phase of meiosis where homologous chromosomes pair up and crossing over occurs.

Metaphase I

The stage in meiosis I where homologous pairs (tetrads) align at the cell's equator.

Anaphase I

The phase in meiosis I where homologous chromosomes separate and move to opposite poles.

Telophase I / Cytokinesis I

The phase where the cell divides to form two haploid cells.

Interkinesis

A short resting phase between meiosis I and meiosis II with no chromosome replication.

Nondisjunction

An error in cell division where chromosomes fail to separate properly, leading to an abnormal number of chromosomes.

Trisomy 21

A genetic condition where an individual has three copies of chromosome 21, causing Down syndrome.

Law of Segregation

The principle that two alleles for the same gene will separate during meiosis and be placed into different gametes.

Law of Independent Assortment

The principle that alleles for different genes assort independently of one another during meiosis.