LEC41: Mitosis and Meiosis Flashcards
what are the steps of mitosis as visualized in the light microscope?
1) prophase
2) prometaphase
3) metaphase
4) anaphase
5) telophase
6) cytokinesis
what do microtubules and actin filaments do during mitosis?
do they have distinct or redundant functions in cell division?
microtubules: form as spindles during promteaphase; attach to the chromosome, anchor it to mitotic spindle, interdigitate with each other from opposite poles
actin: drives cytokinesis, when G1 daughter cells form
in what important way does meiosis differ from mitosis?
Mitosis: process of cell division, from 4N parent to 2 2N daughter cells that are diploid; somatic cells
Meiosis: germ cells; 2N to 1N haploid cells = reductive division; goes through 2 rounds, Meiosis I and II
during what phase of meiosis does recombination btwn maternal & paternal chromosomes occur?
Prophase I
what are the 2 major ways by which genetic recombination occurs during meiosis?
1) chromosomal crossing-over (infinite recombination possibilities)
2) independent assortment (limited, 223 recombination possibilities)
what are phases of cell cycle?
S phase: DNA synthesis
M phase: mitosis, cell division
G1 & G2: “gap” or “growth” phases, cell syntheizing things that aren’t necessary for DNA synthesis (G1) and synthesizing things needed for mitosis (G2)
what is DNA content in each phase of somatic cell cycle?
G1: 2N
S phase: between 2N and 4N
G2: 4N
M phase: 4N
what does human somatic cell alternate beween?
interphase and mitosis
what is mitosis?
process of cell division
go from one 4N G2 cell to 2 2N G1 daughter cells
G2 > prophase, prometaphase, metaphase, anaphase, telophase > G1 + G1
what happens to centrosomes / microtubule organizing centers during S phase?
they double
prophase steps?
first
1) centrosomes (2) move to the poles
2) nuclear membrane breaks down
3) chromosomes condense, become visible
4) each pair of sister chromatids are held together by the centromere
prometaphase steps?
2nd
1) spindle fibers (microtubules) form, attach to the kinetochore
have 3 kinds of microtubules:
1) astrac MT: position at mitotic spindle
2) kinetochore MT: attach to chromosomes
3) polar MT: interdigitate w/ MTs from opposite pole
metaphse steps?
3rd
1) chromosomes align in center of mitotic spingle
2) karyotiping done at this phase
anaphase steps?
4th
1) sister chromatids separate and move to opposite poles
2) cell elongates in preparation for telophase
telphase steps?
5th
1) reformation of nuclear membrane
2) chromosomes decondense (reversal of prophase)
3) spindle, MT, disappear