Cell Division & Differentiation Flashcards
Why do cells grow and divide
- to generate tissues
- to make those tissues grow
- to make up for ‘wear and tear” on those tissues
How do cells grow and divide
- cell division - making a new cell
- hypetrophy - a cell getting physically bigger
Halting cell division causes ___
death
Define ‘cell division’
the process by which cells double their content, then divide to produce 2 daughter cells
State the 3 cycles of the cell cycle
1) chromosome cycle
2) cytoplasmic cycle
3) centrosome cycle
Outline each of the 3 cycles
chromosome cycle
- DNA replication & segregation (mitosis)
cytoplasmic cycle
- organelle replication & physical division (cytokinesis)
centrosome cycle
- replication of the mitotic spindle
State the 3 phases of interphase
1) G1 phase
2) S phase
3) G2 phase
Outline phase 1 of interphase (4)
G1 phase
- start point of the cycle
- G = gap
- normal cell activity
- often the longest phase
Outline phase 2 of interphase (3)
S phase
- S = synthesis
- cell contents double (DNA & cytoplasm)
- chromosomes duplicate to form sister chromatids
Outline phase 3 of interphase (3)
G2 phase
- second gap phase
- normal biosynthesis
- only occurs when all DNA is replicated
State the potential 5th phase (3)
G0
- the cell exits the cell cycle
- normal cellular role, but unlikely to ever divide
State what protein is involved in cell cycle checkpoints
cyclin
State the function of the protein in the cell cycle (2)
- maintain integrity of the replicating genetic material
- if a flaw is found at any single stage, the cell does not progress into the next phase
State 2 diff. cytoskeletal machines involved in mitosis
- mitotic spindle –> microtubules
- contractile ring –> actin & myosin
Describe the 2 cytoskeletal machines
mitotic spindle
- microtubles grow out like points of a star
- formed via duplication of the centrosome during S phase
contractile ring
- consists of both actin & myosin filaments
- forms under plasma membrane at equator of cell
- contracts to divide cell in 2
State the 2 proteins involved in the contractile ring
- actin
- myosin
State the 6 stages of M phase
stages 1-5 = mitosis
1) prophase
2) prometaphase
3) metaphase
4) anaphase
5) telophase
stage 6 = cytokinesis
Outline step 1 of the M phase (2)
prophase
- chromosomes begin to condense
- outside nucleus, mitotic spindles begin to assemble
Outline step 2 of the M phase (4)
prometaphase
- nuclear membrane breaks down
- spindle & chromosomes meet
- attachment via kinetochore
- spindle begins to move to the poles of the cell
Outline step 3 of the M phase (2)
metaphase
- sister chromatids align on cell equator
- metaphase plate forms
Outline step 4 of the M phase (4)
anaphase
- sister chromatids separated by separase (enzyme) (produced in early part of anaphase)
- spindle poles move outwards
- microtubules shorten
- chromosome slides along microtubule
Outline step 5 of the M phase (4)
telophase
- chromosomes arrive at poles
- chromosomes decondense
- nuclear envelope forms
- cells split into 2
Outline step 6 of the M phase (4)
cytokinesis
- starts in anaphase, ends in telophase
- actinomyosin ring assembles under cell membrane
- contraction of the ring pinches cell into 2
- each cell has one full set of chromosoms, a centrosome, & half the cytoplasm
State what phase differentiated cells are in
G0
State what triggers a cell to undergo differentiation (3)
- diffusable factors (signals)
- proteins in ECM
- hormones
Define ‘acetylated tubulin’
a protein that neurons express
State the 2 steps in cell differentiation
- specification
- determination
Outline the 2 steps in cell differentiation (5)
specification
- capable of autonomous differentiation in isolation (if in test tube/dish)
- can be reversed
- not “fate committed”
determination
- cell differentiates into a specific cell type, even when it is placed amongst cells of a diff. type
- irreversible
- “fate committed”
Define ‘terminal differentiation’
when division must cease for differentiation to occur
State examples of cell types which require terminal differentation (2)
- nerves
- skeletal muscle
State what cells which do not require ‘terminal differentiation’ do during division to differentiate
other cell types significantly slow division to differentiate
When can cells de-differentiate? (3)
during regeneration
- some animals can regenerate body parts after injury
- cells at injured site de-differentiate
