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

anaphase stage of mitosis during which sister chromatids are separated from each other

cell cycle ordered sequence of events that a cell passes through between one cell division and the next

cell cycle ordered series of events involving cell growth and cell division that produces two new daughter cells

cell cycle checkpoint mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell cycle stages

cell plate structure formed during plant cell cytokinesis by Golgi vesicles, forming a temporary structure (phragmoplast) and fusing at the metaphase plate; ultimately leads to the formation of cell walls that separate the two daughter cells

centriole rod-like structure constructed of microtubules at the center of each animal cell centrosome

centromere region at which sister chromatids are bound together; a constricted area in condensed chromosomes

chiasmata (singular, chiasma) the structure that forms at the crossover points after genetic material is exchanged

chromatid single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere

cleavage furrow constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division

cohesin proteins that form a complex that seals sister chromatids together at their centromeres until anaphase II of meiosis

condensin proteins that help sister chromatids coil during prophase

crossover exchange of genetic material between non-sister chromatids resulting in chromosomes that incorporate genes from both parents of the organism

cyclin one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle

cyclin-dependent kinase one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation

cytokinesis division of the cytoplasm following mitosis that forms two daughter cells.

diploid cell, nucleus, or organism containing two sets of chromosomes (2n)

diploid-dominant life-cycle type in which the multicellular diploid stage is prevalent

fertilization union of two haploid cells from two individual organisms

G₀ phase distinct from the G₁ phase of interphase; a cell in G₀ is not preparing to divide

G₁ phase (also, first gap) first phase of interphase centered on cell growth during mitosis

G₂ phase (also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis

gamete haploid reproductive cell or sex cell (sperm, pollen grain, or egg)

gametophyte a multicellular haploid life-cycle stage that produces gametes

gene physical and functional unit of heredity, a sequence of DNA that codes for a protein.

genome total genetic information of a cell or organism

germ cells specialized cell line that produces gametes, such as eggs or sperm

haploid cell, nucleus, or organism containing one set of chromosomes (n)

haploid-dominant life-cycle type in which the multicellular haploid stage is prevalent

histone one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes

homologous chromosomes chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent

interkinesis (also, interphase II) brief period of rest between meiosis I and meiosis II

interphase period of the cell cycle leading up to mitosis; includes G₁, S, and G₂ phases (the interim period between two consecutive cell divisions

karyokinesis mitotic nuclear division

kinetochore protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase

life cycle the sequence of events in the development of an organism and the production of cells that produce offspring

locus position of a gene on a chromosome

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

metaphase stage of mitosis during which chromosomes are aligned at the metaphase plate

metaphase plate equatorial plane midway between the two poles of a cell where the chromosomes align during metaphase

mitosis (also, karyokinesis) period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase

mitotic phase period of the cell cycle during which duplicated chromosomes are distributed into two nuclei and cytoplasmic contents are divided; includes karyokinesis (mitosis) and cytokinesis

mitotic spindle apparatus composed of microtubules that orchestrates the movement of chromosomes during mitosis

nucleosome subunit of chromatin composed of a short length of DNA wrapped around a core of histone proteins

p21 cell cycle regulatory protein that inhibits the cell cycle; its levels are controlled by p53

p53 cell cycle regulatory protein that regulates cell growth and monitors DNA damage; it halts the progression of the cell cycle in cases of DNA damage and may induce apoptosis

prometaphase stage of mitosis during which the nuclear membrane breaks down and mitotic spindle fibers attach to kinetochores

prophase stage of mitosis during which chromosomes condense and the mitotic spindle begins to form

quiescent refers to a cell that is performing normal cell functions and has not initiated preparations for cell division

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 non-sister chromatids

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

retinoblastoma protein (Rb) regulatory molecule that exhibits negative effects on the cell cycle by interacting with a transcription factor (E2F)

S phase second, or synthesis, stage of interphase during which DNA replication occurs

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

telophase stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by a new nuclear envelope

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