Meiosis, Sexual Reproduction, and Sex Determination

Vocabulary flashcards covering key terms and definitions from the lecture notes on meiosis, gametogenesis, and mechanisms of sex determination.

Meiosis

The process of division of a eukaryotic nucleus that leads to daughter nuclei that have half the chromosome complement of the parent nucleus, specifically one member of each homologous pair.

Haploid

Describes cells which have only a single set of chromosomes ($n$).

Gamete

A (usually) haploid reproductive cell capable of fusing with another gamete to produce a zygote.

Bivalent

A pair of sister chromatids associated with the homologous pair of sister chromatids, formed during meiosis I.

Crossing Over

A physical exchange of chromosome pieces between homologous chromosomes in a bivalent during meiosis I.

Gametogenesis

The process of producing gametes.

Isogamous

Refers to species in which the gametes are morphologically similar.

Heterogamous

Refers to species that produce two morphologically different types of gametes, typically small mobile sperm cells and larger, less mobile egg cells or ova.

Spermatogenesis and Oogenesis

The processes of gamete production in animals; spermatogenesis produces sperm cells continuously in males during maturity, while oogenesis produces egg cells and polar bodies through interrupted meiotic stages in females.

Sex chromosomes

Chromosomes present in different numbers in males and females.

Autosomes

Chromosomes present in the same number in males and females

Z-W system

A sex determination mechanism in birds where males are homogametic ($76 + ZZ$) and females are heterogametic ($76 + ZW$).

Klinefelter syndrome

A sex chromosome variation resulting in an $XXY$ genotype, occurring in approximately $1 \text{ in } 1{,}000$ births.

Turner syndrome

A sex chromosome variation resulting in an $XO$ genotype, occurring in approximately $1 \text{ in } 5{,}000$ births.

SRY

A male sex-determining gene typically located on the Y chromosome that switches gonad development from ovarian to testicular.

AR

Encodes the androgen receptor, which is critical for cellular response to androgen in producing male traits; XY individuals with loss of this function are female