Meiosis and Sexual Reproduction (OpenStax Biology: Chapter 11)

Sporophyte

A multi-cellular diploid life-cycle stage that produces haploid spores by meiosis.

Gametophyte

A multi-cellular haploid life-cycle stage that produces gametes.

Meiosis

A nuclear division process that results in four haploid cells.

Somatic Cell

All the cells of a multi-cellular organism except the gametes or reproductive cells.

Interkinesis (Also, Interphase 2)

Brief period of rest between meiosis 1 and meiosis 2.

Crossover

Exchange of genetic material between non-sister chromatids resulting in chromosomes that incorporate genes from both parent of the organism.

Meiosis 1

First round of meiotic cell division; referred to as reduction division because the ploidy level is reduced from diploid to haploid.

Synapsis

Formation of a close association between homologeous chromosomes during prophase1, supporting crossover.

Spore

Haploid cell that can produce a haploid multi-cellular organism or can fuse with another spore to form a diploid cell.

Alternation of Generations

Life-cycle type in which the diploid and haploid stages alternate.

Diploid-Dominant

Life-cycle type in which the multi-cellular diploid stage is prevalent.

Haploid-Dominant

Life-cycle type in which the multi-cellular haploid stage is prevalent.

Reduction Division

Nuclear division that produces daughter nuclei each having one-half as many chromosome sets as the parental nucleus; meiosis 1 is a reduction division.

Recombination Nodules

Protein assemblies formed on the synaptonemal complex that marks the points of crossover events and mediate the multi-step process of genetic recombination between non-sister chromatids.

Cohesin

Proteins that form a complex that seals sister chromatids together at their centromeres until anaphase 2 of meiosis.

Meiosis 2

Second round of meiotic cell division following meiosis 1; sister chromatids are separated into individual chromosomes, and as a result is four unique haploid cells.

Germ Cells

Specialized cell line that produces gametes, such as eggs or sperm.

Life Cycle

The sequence of events in the development of an organism and the production of cells that produce offspring.

Ciasmata (Singular: Chiasma)

The structure that forms at the crossover points after genetic material is exchanged.

Tetrad

Two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase 1.

Fertilization

Union of two haploid cells from two different organisms.