Genetics: Meiosis - Reduction Division

Vocabulary flashcards covering key terms and definitions related to meiosis, its stages, and associated cellular components and processes from the lecture notes.

Meiosis

A process of reduction division by which gametes (sex cells) with half the number of chromosomes are produced.

Somatic Cells

Body cells that contain the normal number of chromosomes, known as the 'Diploid' number (2n), such as skin cells or brain cells.

Diploid number (2n)

The normal number of chromosomes in 'body' cells, meaning two chromosomes in the set.

Gametes

Sex cells that contain only half the normal number of chromosomes, known as the 'Haploid' number (n), such as sperm cells and ova.

Haploid number (n)

The number of chromosomes in gametes, meaning one chromosome in the set.

Polyploid cells

Cells that have more than two chromosomes per set, for example, 3n (3 chromosomes per set).

Male Gamete

The sperm, produced in the male gonad called the Testes.

Female Gamete

The ovum (ova = plural), produced in the female gonad called the Ovaries.

Ovulation

The process during which the ovum is released from the ovary and transported to an area where fertilization can occur.

Fertilization

The joining of the sperm and ovum, resulting in the formation of a zygote (fertilized egg). In humans, it occurs in the fallopian tube.

Zygote

A fertilized egg, formed by the fusion of a sperm and an egg.

Homologues

Matching chromosomes, one from the mother and one from the father, each carrying their respective DNA.

Homologous Chromosomes

A pair of chromosomes (maternal and paternal) that are similar in shape and size, carrying genes controlling the same inherited traits.

Locus

The position of a gene on a chromosome, which is in the same position on homologous chromosomes.

Autosomes

The 22 pairs of non-sex chromosomes in humans.

Sex chromosomes

The 1 pair of chromosomes in humans that determine sex.

Tetrad

A homologous pair of chromosomes consisting of four chromatids (sister and nonsister chromatids).

Meiosis I (Reduction Stage)

The first cell division in meiosis that reduces the chromosome number by one-half.

Meiosis II (Division Stage)

The second cell division in meiosis that produces four haploid daughter cells.

Spermatogenesis

The process of meiosis in males that produces sperm.

Oogenesis

The process of meiosis in females that produces ova.

Interphase I of Meiosis

A phase similar to mitosis interphase where chromosomes replicate (S phase), and each duplicated chromosome consists of two identical sister chromatids attached at their centromeres; centriole pairs also replicate.

Prophase I

The longest and most complex phase of Meiosis I, where chromosomes condense, and synapsis occurs to form tetrads.

Synapsis

The process where homologous chromosomes come together to form a tetrad during Prophase I.

Crossing Over

The exchange of chromosome segments between non-sister chromatids during Prophase I, which spreads variation through a population.

Chiasmata (Chiasma)

The sites where crossing over occurs between non-sister chromatids.

Metaphase I

The shortest phase of Meiosis I, where tetrads align on the metaphase plate.

Anaphase I

The phase of Meiosis I where homologous chromosomes separate and move towards the poles, while sister chromatids remain attached at their centromeres.

Telophase I

The phase of Meiosis I where each pole has a haploid set of chromosomes, followed by cytokinesis which forms two haploid daughter cells.

Meiosis II

The second stage of meiosis, similar to mitosis, occurring after Meiosis I without an interphase II.

Prophase II

The first phase of Meiosis II, which is the same as prophase in mitosis.

Metaphase II

The phase of Meiosis II where chromosomes align on the metaphase plate, similar to metaphase in mitosis.

Anaphase II

The phase of Meiosis II where sister chromatids separate and move towards opposite poles, similar to anaphase in mitosis.

Telophase II

The final phase of Meiosis II where nuclei form, cytokinesis occurs, and four haploid daughter cells (gametes) are produced.