BIO 311C - Cell Division
metaphase
-centrosomes appear at opposite ends of the cell -chromosomes convene at the metaphase plate
prophase
-chromatin condense into chromosomes -nucleolus disappears -mitotic spindle forms -centrosomes move away from each other
prophase I
-chromosomes condense -centrosome movement -NEBD -spindle forms -homologs synapse (connect), forming chiasma -microtubules attach to kinetochores and move homologs toward metaphase plate
telophase I
-each half of cell has a complete haploid set of duplicated chromosomes -cleavage furrow (animals)/cell plate (plants) forms -cytokinesis follows
prometaphase
-nuclear envelope breaks down -chromatids joined by kinetochores - can interact with microtubules
telophase
-nuclei reform in daughter cells -microtubules depolymerize
anaphase
-shortest phase -chromatids separate to form full chromosomes
prophase II
-spindle forms -chromosomes move toward metaphase plate
checkpoints
G1 (restriction point) - checks environment G2 - checks DNA replication/damage M - checks chromosomes and spindle
MPF
M-Phase Promoting Factor = triggers past G2 checkpoint --> M phase (phosphorylates nuclear lamina to fragment nuclear envelope during prometaphase)
binary fission
cell division in prokaryotes; DNA replication occurs at the origin of circular chromosomes, which causes cell elongation; microfilaments and microtubules are used for chromosome movement and membrane pinch
duplicated chromosomes
consist of 2 sister chromatids; separate during mitosis
interphase
consists of G1, S, & G2 phases in the cell cycle; 90% of the cycle; alternates with M-phase
M-phase
consists of mitosis and cytokinesis; alternates with interphase
haploid
containing 1 set of chromosomes (n in humans = 23)
diploid
containing 2 sets of chromosomes (2n in humans=46)
mitotic cell division
creates 2 haploid daughter cells with identical DNA
meiotic cell division
creates 4 haploid daughter cells with a mix of maternal and paternal DNA
alleles
different versions of genes on each homolog
mitosis
division of genetic material in the nucleus
cytokinesis
division of the cytoplasm
elongation of cell
done by nonkinetochore microtubules as motor proteins walk away on them
gametes
eggs or sperm in humans that undergo meiosis and contain 23 chromosomes in humans
independent assortment
either homologous pair can line up on either side of the metaphase plate in metaphase I
kinases
enzymes that activate proteins by phosphorylation; at G1 and G2; exist in *constant concentration throughout cell*
mitotic spindle
fibers from microtubules and associated proteins; forms in cytoplasm during prophase; elongates by polymerizing, shortens by depolymerizing
G1
first gap phase = cell growth (checkpoint too)
cell plate
forms in plant cells from vesicles in cytosol
anaphase I
homologs separate
crossing over
in prophase I, nonsister chromatids exchange corresponding DNA segments
sister chromatids
joined pairs of replicated DNA molecules making up a chromosome; separate during mitosis
cyclin-dependent kinase (Cdk)
kinases need cyclin to work
contractile ring
microfilaments interact with myosin, pinching the parent cell in half
centrosome
microtubule organizing center (MTOC)
separation of chromosomes
microtubules pull sister chromatids in opposite directions
regulation of the cell cycle
molecules trigger/coordinate events in the cell cycle control system - a series of checkpoints
nonsister chromatids
not joined with centromere; 1 maternal + 1 paternal
telophase II
nuclei reform, chromosomes condense, cytokinesis follows results in 4 daughter cells with one set of unduplicated chromosomes each
homologous chromosomes (homologs)
one maternal + one paternal chromosome that pair up during meiosis
cleavage
process by which cytokinesis occurs - forms cleavage furrow = shallow groove near the old metaphase plate
meiosis I
produces haploid (n) cells with duplicated chromosomes
meiosis II
produces haploid (n) cells with unduplicated chromosomes
anaphase II
proteins break down, causing sister chromatids to separate and move toward opposite poles of the cell
meiosis
reduces number of chromosomes from diploid to haploid (2n --> n)
centromeres
regions with specific DNA sequences where chromatids attach most closely
G2
second gap phase = cell growth; right before M-phase (checkpoint too)
S phase
synthesis phase = DNA replication
kinetochore
the proteins on each sister chromatid at each centrosome; face oppositely; the location where spindle microtubules can attach during prometaphase
metaphase II
unidentical chromatid pairs line up at plate; microtubules attach to *chromatid* kinetochores
metaphase I
*homologous pairs* at metaphase plate
sex chromosome
X and Y chromosomes that determine gender
autosome
a chromosome that is not a sex chromosome
cyclin
a protein whose concentration fluctuates throughout the cell
somatic cells
all body cells excluding gametes (sex cells); contain 46 chromosomes in humans