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