SBP Meiosis and Mitosis

Homologous Chromosomes

two separate chromosomes one from mother and one from father; same length and carry the same genes.

Sister Chromatids

two identical copies of a single replicated chromosome attached at a single centromere.

Meiosis

a type of cell division that creates 4 haploid cells from one diploid cell.

Haploid

a cell that contains one set of chromosomes.

Diploid

a cell that contains two sets of chromosomes.

Gamete

a sex cell (sperm or egg).

Zygote

the cell formed by the fusion of two gametes.

Crossing Over

the exchange of genetic material between non-sister chromatids of homologous chromosomes.

Synapsis

the pairing of homologs to form a tetrad.

Tetrad

a tight grouping of two chromosomes, each consisting of two sister chromatids (paired maternal and paternal homologous chromosomes).

Chiasma

the site of crossing-over.

Prophase I

the first stage of meiosis I where chromosomes condense, homologous chromosomes pair, and crossing over occurs.

Metaphase I

the stage of meiosis I where homologous chromosomes line up at the equator.

Anaphase I

the stage of meiosis I where homologous chromosomes separate and move to opposite poles.

Telophase I

the stage of meiosis I where chromosomes reach opposite ends, nuclear membranes may reform, and cytokinesis occurs.

Meiosis II

the second division in meiosis, where sister chromatids are separated.

Prophase II

the first stage of meiosis II where chromosomes condense and the nuclear envelope breaks down.

Metaphase II

the stage of meiosis II where chromosomes line up single file at the equator.

Anaphase II

the stage of meiosis II where sister chromatids separate and move to opposite poles.

Telophase II

the final stage of meiosis II where nuclear membranes reform around the separated chromosomes.

Cytokinesis

the division of the cytoplasm to form separate daughter cells.

Spermatogenesis

the process of sperm cell development in males.

Oogenesis

the process of egg cell development in females.

Polar Body

a small, nonfunctional cell produced during oogenesis that eventually breaks down.

Genetic Variation

differences in the genetic makeup of individuals.

Independent Assortment

the random arrangement and separation of homologous chromosomes during metaphase I.

Genetic Linkage

the tendency for genes located close together on a chromosome to be inherited together.

Nondisjunction

the failure of homologous chromosomes or sister chromatids to separate properly during meiosis.

Aneuploidy

a condition where an individual has an abnormal number of chromosomes.

Trisomy

a type of aneuploidy where an individual has three copies of a particular chromosome.

Down Syndrome

a condition caused by trisomy of chromosome 21.

Patau Syndrome

a condition caused by trisomy of chromosome 13.

Edward's Syndrome

a condition caused by trisomy of chromosome 18.

Klinefelter Syndrome

a condition in males caused by an extra X chromosome (47,XXY).

Turner Syndrome

a condition in females caused by having only one X chromosome (45,X).