CH 11 Meiosis & Sexual Reproduction

alternation of generations

life-cycle type in which the diploid and haploid stages alternate

chiasmata

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

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

tetrad

two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase I