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45 terms

Chapter 5: Mitosis and Meiosis

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somatic cells
cells of the body, other than those of the ovaries and testes
sex cells
gametes; egg and sperm
mitosis
division of the nucleus
cytokinesis
division of the cytoplasm
apoptosis
programmed cell death
interphase
phase of cell cycle composed of G1, S and G2
growth factors
hormones that act as external signals binding at the plasma membrane
cyclins
protein molecules which act as internal signals for the phases of the cell cycle
p53 protein
a protein coded for by the p53 gene that stops the cell cycle at the G1 checkpoint if DNA is damaged
p53 gene
a gene on a chromosome which codes for the p53 protein
caspases
enzymes that cause apoptosis
chromatin
DNA in a non-dividing cell which takes the form of long threads not visible under a light microscope
chromosomes
DNA which condenses into distinct structures seen during mitosis and meiosis
S phase
phase of interphase during which DNA replication takes place
G1 phase
phase of interphase during which doubling of organelles takes place
G2 phase
phase of interphase; synthesis of proteins needed for cell division occurs.
diploid
2n; the total number of chromosomes in somatic cells
haploid
n; the number of chromosomes in an egg or sperm
prophase
phase of mitosis; nuclear envelope disappears, chromosomes become visible, spindle fibers form
metaphase
phase of mitosis; chromosomes line along equator of cell
anaphase
phase of mitosis; centromeres replicate, sister chromosomes move into opposite poles of cell
telophase
phase of mitosis; nuclear envelope reassembles, cytokinesis begins
cleavage furrow
pinching of animal cells that occurs during cytokinesis
cell plate
forms in plant cells during cytokinesis
meiosis
cell division in which the chromosome number is reduced by half
duplicated chromosome
chromosome which has two sister chromatids joined by a centromere
centromere
a structure which joins two sister chromatids
synapsis
the pairing of homologous chromosomes that occurs during prophase I
reduction division
meiosis I (chromosoe number goes from diploid to haploid)
fertilization
joining of egg and sperm; forms the zygote
zygote
the diploid cell that results from the fusion of egg and sperm at fertilization
crossing over
the exchange of genetic information which occurs during synapsis, during prophase I
independent assortment
the random movement of maternal and paternal chromosomes along the metaphase plate during Metaphase I; causes genetic variability
interkinesis
the period of time between meiosis I and II
nondisjunction
the failure of homologous chromosomes to separate during Anaphase I or failure of sister chromatids to separate in Anaphase II
Down syndrome
trisomy 21; a result of nondisjunction
Turner's syndrome
a female with only one X chromosome; caused by nondisjunction. Egg of mother or sperm of father was missing an X Chromosome
spermatogenesis
meiosis in males
oogenesis
meiosis in females
primary spermatocyte
a diploid cell; divides during Meiosis I into 2 secondary spermatocytes
secondary spermatocyte
a haploid cell; divides during meiosis II forming spermatids
spermatozoa
mature sperm cells
primary oocyte
a diploid cell; divides during meiosis I into a secondary oocyte and the first polar body
secondary oocyte
haploid cell; divides during meiosis II into an ovum and another polar body
ovum
mature eff produced by female