Chapter 8 Mitosis and Meiosis

anaphase

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

aneuploid

an individual with an error in chromosome number; includes deletions and duplications of chromosome segments

autosome

any of the non-sex chromosomes

binary fission

the process of prokaryotic cell division

cell cycle

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

cell cycle checkpoints

mechanisms that monitor the preparedness of a eukaryotic cell to advance through the various cell cycle stages

cell plate

a structure formed during plant-cell cytokinesis by Golgi vesicles fusing at the metaphase plate; will ultimately lead to formation of a cell wall to separate the two daughter cells

centriole

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

chromosome inversion

the detachment, 180° rotation, and reinsertion of a chromosome arm

chromosomal translocation

a segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome

cleavage furrow

a constriction formed by the actin ring during animal-cell cytokinesis that leads to cytoplasmic division

crossing over

(also, recombination) the exchange of genetic material between homologous chromosomes resulting in chromosomes that incorporate genes from both parents of the organism forming reproductive cells

cytokinesis

the division of the cytoplasm following mitosis to form two daughter cells

diploid

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

euploid

an individual with the appropriate number of chromosomes for their species

fertilization

the union of two haploid cells typically from two individual organisms

G0 phase

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

G1 phase

(also, first gap) a cell-cycle phase; first phase of interphase centered on cell growth during mitosis

G2 phase

(also, second gap) a cell-cycle phase; third phase of interphase where the cell undergoes the final preparations for mitosis

gamete

a haploid reproductive cell or sex cell (sperm or egg)

gene

the physical and functional unit of heredity; a sequence of DNA that codes for a specific peptide or RNA molecule

genome

the entire genetic complement (DNA) of an organism

germ cell

a specialized cell that produces gametes, such as eggs or sperm

haploid

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

homologous chromosomes

chromosomes of the same length with genes in the same location; diploid organisms have pairs of homologous chromosomes, and the members of each pair come from different parents

independent assortment

during metaphase I of meiosis, homologous chromosome pairs separate randomly into cells

interphase

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

karyogram

the photographic image of a karyotype

karyotype

the number and appearance of an individuals chromosomes, including the size, banding patterns, and centromere position

kinetochore

a protein structure in 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

ligands

chemical messages released from other cells, and if they are polar, they must bind to receptors to get their message into cells

locus

the position of a gene on a chromosome

meiosis

a nuclear division process that results in four haploid cells

meiosis I

the first round of meiotic cell division; referred to as reduction division because the resulting cells are haploid

meiosis II

the second round of meiotic cell division following meiosis I; sister chromatids are separated from each other, and the result is four unique haploid cells

metaphase

the stage of mitosis during which chromosomes are lined up at the metaphase plate

metaphase plate

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

mitosis

the period of the cell cycle at which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase

mitotic phase

the period of the cell cycle when duplicated chromosomes are distributed into two nuclei, and the cytoplasmic contents are divided; includes mitosis and cytokinesis

mitotic spindle

the microtubule apparatus that orchestrates the movement of chromo-

somes during mitosis

monosomy

an otherwise diploid genotype in which one chromosome is missing

nondisjunction

the failure of synapsed homologs to completely separate and migrate to separate poles during the first cell division of meiosis

origin

the region of the prokaryotic chromosome at which replication begins

partial chromosomal deletion

the deletion or removal of a portion of a chromosome

partial chromosomal duplication

a portion of a chromosome is duplicated or multiple copies of that section are present

polyploid

an individual with an incorrect number of chromosome sets

prometaphase

the stage of mitosis during which mitotic spindle fibers attach to kinetochores

prophase

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

quiescent

describes a cell that is performing normal cell functions and has not initiated preparations for cell division

receptors

transmembrane proteins that bind ligands

recombinant

describing something composed of genetic material from two sources, such as a chromosome with both maternal and paternal segments of DNA

S phase

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

sex chromosomes

those involved with determining the sex of an individual, X and Y in humans and other mammals

signal transduction cascade

a series of intracellular proteins which are activated by a change in receptor shape after binding to a ligand

sister chromatids

two identical copies of each chromosome formed by DNA replication

somatic cell

all the cells of a multicellular organism except the gamete-forming cells

synapsis

the formation of a close association between homologous chromosomes during prophase I

telophase

the stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by new nuclear envelopes

tetrad

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

translocation

the process by which one segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome

trisomy

an otherwise diploid genotype in which one entire chromosome is duplicated

X inactivation

the condensation of X chromosomes into Barr bodies during embryonic development in females to compensate for the double genetic dose