Chapter 10: Meiosis and Sexual Reproduction

Vocabulary terms and definitions related to Meiosis and Sexual Reproduction, covering chromosome types, cell cycle stages, and the phases of meiosis I and II.

Meiosis

A type of nuclear division in sexually reproducing organisms that reduces the chromosome number of the cell by $50\%$.

Haploid ($n$)

The number of chromosomes representing a single set; in humans, this number is $23$.

Diploid ($2n$)

The total number of chromosomes in a cell, reflecting two sets of each chromosome; in humans, this number is $46$.

Gametes

Reproductive cells, such as sperm and egg cells, which usually have the haploid number of chromosomes.

Zygote

A diploid cell formed during sexual reproduction when haploid gametes merge.

Cell cycle

A series of events involving growth and division, where a cell spends most of its time in interphase before undergoing mitosis or meiosis.

Interphase

The phase of the cell cycle during which the cell grows, replicates its chromosomes in the S stage, and prepares for division.

Homologous chromosomes (homologues)

Pairs of chromosomes of the same type that have the same length, centromere position, and similar banding patterns.

Karyotype

A preparation of the complete set of metaphase chromosomes in an organism, sorted by length, centromere location, and other features.

Autosomes

The human chromosomes numbered $1$ through $22$.

Synapsis

The process during Meiosis I where homologous chromosomes pair up and align side by side.

Meiosis I

The first nuclear division where homologous pairs separate and the chromosome number is reduced from $2n$ to $n$.

Meiosis II

The second nuclear division where sister chromatids separate, resulting in four haploid daughter cells.

Interkinesis

The period between Meiosis I and Meiosis II during which DNA is not replicated and chromosomes still consist of two chromatids.

Prophase I

The phase of Meiosis I where homologous chromosomes pair during synapsis.

Metaphase I

The phase of Meiosis I where homologous chromosome pairs align at the metaphase plate.

Anaphase I

The phase of Meiosis I where homologous chromosomes separate and are pulled to opposite poles by centromeric spindle fibers.

Telophase I

The phase of Meiosis I ending with daughter cells that have one duplicated chromosome from each homologous pair.

Prophase II

The phase of Meiosis II where cells have one chromosome from each homologous pair.

Metaphase II

The phase of Meiosis II where individual chromosomes align at the metaphase plate.

Anaphase II

The phase of Meiosis II where sister chromatids separate and daughter chromosomes move toward the poles.

Telophase II

The final phase where the spindle disappears, nuclei form, and cytokinesis takes place, resulting in four haploid daughter cells.