Genetics
Mitosis
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Get access- Each chromosome replicates
- Daughter cells are formed with 46 chromosomes (diploid)
- Most mammalian cells have a cell cycle of 24 hours:
- G0 stage where the cell is quiescent
- Some cell types are permanently stopped in G0.
- M stage: mitosis occupies 1 hour
- Vincristine acts on tubulin which is essential during this phase
- G1: first gap phase with biosynthetic activity (variable duration)
S phase: synthesis of DNA and chromosomal replication to form two daughter chromatids (6-8 hours)
- Methotrexate is a dihydrofolate reductase inhibitor active during this phase
G2: second gap phase with preparation for division (cell almost doubles its total mass before the next mitosis)
- Interphase: resting
- This comprises G1, S and G2.
- The following phases are all within M (mitosis)
- Prophase: chromosome condense and become visible
- Nucleolus disappears
- Mitotic spindles form
- Kinetochores at the centromeres facilitate attachment to the microtubules
- Metaphase: chromosomes aligned in the equatorial plane
- Anaphase: centromere divides with chromatid separation at the centromere
- Chromatids move to opposite poles of the cell
- Telophase: reformation of the nuclear membranes
- Decondensation of the chromosomes
- Cytokinesis (division of the cytoplasm)
- Cyclins:
- Regulatory subunits within cells regulating cyclin-dependent kinases (CDK)
- Nine different examples
Drive the cell through the stages of the cell cycle via phosphorylation of protein substrates
- Retinoblastoma protein is one substrate