108 Key Terms
- alternation of generations
- life-cycle type in which the diploid and haploid stages alternate
- chiasmata
- (singular, chiasma) the structure that forms at the crossover points after genetic material is exchanged
- cohesin
- proteins that form a complex that seals sister chromatids together at their centromeres until anaphase II of meiosis
- crossover
- exchange of genetic material between nonsister chromatids resulting in chromosomes that incorporate genes from both parents of the organism
- fertilization
- union of two haploid cells from two individual organisms
- gametophyte
- a multicellular haploid life-cycle stage that produces gametes
- germ cells
- specialized cell line that produces gametes, such as eggs or sperm
- interkinesis
- (also, interphase II) brief period of rest between meiosis I and meiosis II
- life cycle
- the sequence of events in the development of an organism and the production of cells that produce offspring
- meiosis
- a nuclear division process that results in four haploid cells
- meiosis I
- first round of meiotic cell division; referred to as reduction division because the ploidy level is reduced from diploid to haploid
- meiosis II
- second round of meiotic cell division following meiosis I; sister chromatids are separated into individual chromosomes, and the result is four unique haploid cells
- recombination nodules
- protein assemblies formed on the synaptonemal complex that mark the points of crossover events and mediate the multistep process of genetic recombination between nonsister chromatids of a homologous pair
- reduction division
- nuclear division that produces daughter nuclei each having one-half as many chromosome sets as the parental nucleus; meiosis I is a reduction division
- somatic cell
- all the cells of a multicellular organism except the gametes or reproductive cells
- spore
- haploid cell that can produce a haploid multicellular organism or can fuse with another spore to form a diploid cell
- sporophyte
- a multicellular diploid life-cycle stage that produces haploid spores by meiosis
- synapsis
- formation of a close association between homologous chromosomes during prophase I
- synaptonemal complex
- protein lattice that forms between homologous chromosomes during prophase I, supporting crossover
- tetrad
- two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase I
