ch. 3 mitosis Flashcards
what is cell division regulated by
control of cell cycle
cell cycles of all _____________ are similar
eukaryotes
2 main parts of cell cycle
- M phase - mitosis, cell divides
- interphase - time between M phases
subphrases of interphase
- Gap 1 (G1)
- Resting phase (G0)
- S phase
- Gap 2 (G2)
Gap 1 phase
- all proteins for normal cell function are transcribed and translated
G0 phase
- differentiated cells
- some cells enter G0 after G1
do cells in G0 reenter cell cycle?
no - rarely
S phase
- DNA is replicated
- 2 sister chromatids produced for each chromosome
G2 phase
- cells prepare for division
substages of M phase
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
what does the M phase accomplish?
- karyokinesis
- cytokinesis
karyokinesis
dividing the DNA
cytokinesis
dividing the cell/cytoplasm
are cells at the beginning of mitosis diploid or haploid?
diploid
composition of chromosome after S phase
2 identical sister chromatids
- amount of genetic material doubled
where does condensation of chromosomes begin
prophase
where does maximum condensation of chromosomes occur
metaphse
centromeres
specialized sequences where sister chromatids are joined
what do centromeres bind?
protein complexes called kinetochores
the moment two sister chromatids separate, they are considered…
2 separate chromosomes
centrosomes
nucleate spindle fiber microtubules
- migrate to form opposite poles of dividing cell
where are centrosomes found?
animal cells
what end of the microtubule is at the centrosome?
minus (-)
what end of the microtubule is at the kinetochores?
plus (+)
aster
pattern in which spindle fibers emanate from the centrosomes
types of microtubules in cells
- kinetochore
- polar
- astral
kinetochore microtubules
- centrosome to kinetochore
- move chromosomes during cell division
polar microtubules
- centrosome to centrosome
- cell elongation and stability
- “non-kinetochore microtubules”
astral microtubules
- centrosome to membrane
- cell stability and shape
what does sister chromatid cohesin balance?
tension created by pull of kinetochore microtubules
cohesin
4-subunit protein complex that coats sister chromatids along their entire length to hold them together
- prevents premature separation
where is highest concentration of cohesin?
centromeres
what happens in anaphase?
sister chromatids separate and begin to move toward opposite poles in the cell
what causes sister chromatids to separate in anaphase A?
action of enzyme Separase
separase
cleaves Scc1, a central component of cohesin complex
- causes disjunction
disjunction
separation of sister chromatids
non-disjunction
failure of sister chromatids to properly separate
- causes chromosomal number mutations
what do polar microtubules do during anaphase
extend in length, which will later allow cytokinesis
what do kinetochore microtubules do during anaphase
shorten
- depolymerize at their plus end, moving individual chromatids toward centrioles/opposite poles
what happens in telophase
- nuclear membranes reassemble around chromosomes at each pole
- chromosomes de-condense
- 2 identical nuclei occupy elongated cell, which will soon undergo cytokinesis
cytokinesis in animal cells
- contractile ring of actin creates cleavage furrow around circumference of cell
- pinches cell in 2
- begins on edges and moves inward
cytokinesis in plants
- new cell wall is constructed along cellular midline (cell plate)
- begins in middle and moves outward
what does mitosis produce?
2 identical daughter cells
are the daughter cells genetically identical?
yes
do cells ever become haploid during mitosis?
no
cell cycle checkpoints
monitored by protein interactions for readiness to progress to next stage
mutations altering normal cell cycle control are linked to what?
various cell growth abnormalities
cancer is often characterized by what?
out-of-control proliferation of cells that can invade and displace normal cells
G1 checkpoint
pass if:
- cell size adequate
- nutrient availability is sufficient
- growth factors present
S-phase checkpoint
pass if:
- DNA replication is complete
- screened to remove base-pair mismatch error
G2 checkpoint
pass if:
- cell size is adequate
- chromosomes replication completed
metaphase checkpoint
pass if:
- all chromosomes attached to mitotic spindle
