Gametes - Cell Cycle Flashcards
What is the duration of skin cell cycle
12-24 hours
Describe the nature of cell cycle with liver cells
- Transient withdrawal from the cell cycle
- Temporarily disassemble cell cycle control system
- Retain ability to reassemble control system quickly to re-enter cycle
- Divide once every year or 2 - rapidly with liver damage
Frequency of cell division with mature nerve & muscle cells
- DO NOT divide at all after maturity
- Terminally differentiated in G0 state
What is the frequency of cell division of other cells (e.g. some lymphocytes)
Withdraw and re-enter cell cycle repeatedly
Abbreviations for interphase
What is happening during interphase
How much of cell division does it account for
G1, S, G2
Growth & cell division
Cells spend about 90% of time interphase
What is the abbreviation for the mitotic phase
What is happening during this phase
M
Cell division
What is another name for the quiescent phase
Senescent (G0)
Where is there greatest variation in cell-cycle length
G1 or G0
How long does it take to go from S to M phase in mammals
Is this value constant
12-24 hours
relatively constant, regardless of interval from 1 division to the next
What sort of capacity do embryonic stem cells have
What is their cell cycle characterised by
- Have the capacity for unlimited proliferation
- They retain the potential for differentiation
- Characterised by shotr GI phase and a high proportion of cells in S phase
G0 phase
- Terminally differentiated cells withdraw from cell cycle indefinitely
- Reentry point - a cell returing from G0 enters at early G1 phase
G1 phase
- RNA and protein synthesis
- No DNA synthesis
- 6-12 hours
Restriction point after G1
- A cell that passes this point is committed to pass into S phase
S phase
- DNA synthesis doubles the amount of DNA in the cell
- RNA and protein also synthesized
- 6-8 hours
G2 phase
- No DNA synthesis
- RNA and protein synthesis continue
- 3-4 hours
M phase
- Mitosis (nuclear division) and cytokinesis (cell division) yield 2 daughter cells
- 1 hr
Differentiate mitosis from cytokinesis
MITOSIS = nuclear division
CYTOKINESIS = cell division
Name the 3 phases of interphase
G1, S and G2
Explain the events of the G1 phase
- Recovery from previous division
- Cell doubles its organelles
- Cell grows in size
- Accumulates raw materials for DNA synthesis (DNA replication)
Explain the events of the S phase (of interphase)
- DNA replication
- Proteins associated with DNA are synthesised
- Chromosomes enter with 1 chromatid each
- Chromosomes leave with 2 identical chromatids each
Explain the events of the G2 phase
- Between DNA replication and onset of mitosis
- Cell synthesises proteins necessary for division
What is a chromatid
Define mitosis
Process of nuclear division in eukaryotic cells that occurs when a parent cell divides to produce 2 identical daughter cells
Describe PROPHASE
- Disappearance of nuclei
- Chromatin fibres condense into discrete chromosomes composed of 2 identical sister chromatids joined at a centromere
- Formation of mitotic spindle, composed of microtubules between the 2 centrosomes
- Centrosomes move apart
Describe PRO-METAPHASE
- Nuclear envelope fragments and dissolves
- Spindle fibres extend from each pole towards the cell equator
- Kinetochores form at the centromere
- Kinetochore microtubules attach to the chromosomes