Meiosis: The Process of Reduction Division

This set of vocabulary flashcards covers the fundamental concepts, chromosomal structures, and specific stages of Meiosis I and II as detailed in the lecture.

Meiosis

A process of cell division in sexually mature organisms that forms gametes, starting with a diploid cell ($46$ chromosomes) and ending with haploid cells ($23$ chromosomes).

Reduction division

Another name for meiosis, referring to the process where the chromosome number is reduced by half.

Equation division

Another name for mitosis, where the cell divides into identical diploid cells ($23$ pairs) for growth, development, and repair.

Somatic cells

Body cells that divide using mitosis and contain a diploid number of chromosomes ($46$ in humans).

Homologous chromosomes

Matching pairs of chromosomes in diploid organisms that share the same length, centromere position, and gene sequence, but carry different versions of those genes (alleles).

Gene

A portion of DNA that determines a certain trait.

Allele

A specific form or version of a gene.

Sister chromatid

One of two identical copies of a single chromosome created during the S phase of Interphase, held together at the centromere.

Autosomes

The first $22$ pairs of human chromosomes that are not involved in determining sex.

Sex chromosomes

The $23^{rd}$ pair of chromosomes (XX in females, XY in males) that differ between the sexes.

Diploid

Cells having homologous chromosomes (two genes for each trait), symbolized by $2N$, which include all somatic cells.

Haploid

Cells with only one set of chromosomes (one gene for each trait), symbolized by $N$, which are the result of meiosis.

Synapsis

The tight pairing of homologous chromosomes that occurs during Prophase I.

Crossing-over

The exchange of genetic materials between homologous chromosomes during Prophase I.

Tetrad

The structure formed when homologous chromosomes bind firmly together along their length during Prophase I.

Chiasmata

The points formed by cross-over recombination between non-sister chromatids.

Independent or Random assortment

The process where homologous chromosomes randomly assemble at the metaphase plate during Metaphase I.

Anaphase I

The stage of meiosis where spindle microtubules pull homologous chromosomes apart while sister chromatids remain attached at the centromere.

Cleavage furrow

The structure that forms to divide the cytoplasm during Telophase I and Telophase II.

Interkinesis

A brief resting phase directly after Cytokinesis I where no DNA replication occurs before the cell proceeds to Meiosis II.

Anaphase II

The stage where sister chromatids are pulled apart by the shortening of kinetochore microtubules.

Cytokinesis II

The final stage where the two cells from Meiosis I are divided into four unique haploid daughter cells.