Chapter 10 - Meiosis and Sexual Reproduction

Fundamentals of biology

Euchromatin

Loosely coiled, active chromatin that can be transcribed by RNA polymerase and transcription factors.

Heterochromatin

Tightly coiled, inactive chromatin where genes are hardly ever transcribed.

Interphase

The phase of the cell cycle divided into three stages: G1 (Gap), S (Synthesis), and G2 (Gap 2).

G1 Phase

First gap phase where the cell performs its everyday functions.

S Phase

Synthesis phase of interphase where DNA is replicated.

G2 Phase

Second gap phase where the cell prepares for division by growing and producing organelles.

Cell Cycle

The life cycle of a cell consisting of G1, S, G2, and M phases.

Meiosis

Special cell division in sexually reproducing organisms that reduces diploid (2n) cells to haploid (n) gametes.

Meiosis I

The first division of meiosis where homologous chromosomes separate.

Meiosis II

The second division of meiosis where sister chromatids separate.

Crossing Over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis.

Euploidy

The correct number of chromosomes in a species for multiples of that set.

Aneuploidy

A change in the chromosome number resulting from nondisjunction.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate normally during cell division.

Monosomy

A condition where a zygote has only one copy of a particular chromosome.

Trisomy

A condition where a zygote has three copies of a particular chromosome.

Turner Syndrome (X0)

A condition in females characterized by the presence of a single X chromosome.

Klinefelter Syndrome (XXY)

A condition in males involving an extra X chromosome, leading to underdeveloped testes.

Spermatogenesis

The production of sperm cells through meiosis.

Oogenesis

The production of egg cells, where one of the four nuclei becomes the egg and the others become polar bodies.

Genetic Variation

Differences in DNA that can occur as a result of mutations and recombination during meiosis.

Gametes

Haploid cells produced through meiosis that fuse during fertilization to form a diploid zygote.

Zygote

A diploid cell formed from the fusion of two haploid gametes.