Genes

A gene is a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Homologous Chromosomes

Homologous chromosomes are a pair of chromosomes containing a maternal and paternal chromatid joined to together at the centromere. The have the exact same gene, although may have different alleles of these genes.

Alleles

Alleles are one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Haploid

Haploid is the term used when a cell has half the usual number of chromosomes. A normal eukaryote organism is composed of diploid cells, one set of chromosomes from each parent.

Meiosis

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is required to produce egg and sperm cells for sexual reproduction.

Prophase I

Prophase I is when pairs of homologous chromosomes intertwine and the process called crossing over occurs as chromatids from homologous pairs of chromosomes swap genetic information.

Metaphase I

In metaphase I, the spindle draws the chromosomes to the metaphase plate.

Anaphase I

In anaphase I, the sister chromatids of each chromosome separate and move toward opposite poles.

Telophase I

In telophase I, the chromosomes reach opposite poles, cytokinesis occurs, the two cells produced by meiosis I divide to form four haploid daughter cells, and nuclear envelopes form.

Prophase II

In prophase II, the nuclear envelope breaks down and the spindle apparatus forms.

Metaphase II

In metaphase II, the spindle again draws the chromosomes to the metaphase plate in each of the two daughter cells.

Anaphase II

In anaphase II, the sister chromatids of each chromosome separate and move toward opposite poles.

Telophase II

In telophase II, the chromosomes reach opposite poles, cytokinesis occurs, the two cells produced by meiosis I divide to form four haploid daughter cells, and nuclear envelopes form.