New cells replicate an existing cells, growth occurs before division to turn one zygote to 26 billion cells needed for a baby.
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G1
Growth occurs, makes more proteins and organelles
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S
Genome is replicated, normally the longest phase
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G2
More growth and protein synthesis
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M
Mitosis where cytoplasmic division occurs
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Mitogen
Chemical substance that encourages cells to commence cell division, triggering mitosis. Normally a protein. Activates cyclin-CDK complex formation
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G0
Quinescent/resting state. Cardiomyocytes are permanently in this state
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Growth factors
Increase cell size.
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EGT & TGTa
Blastocyst development
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FGF
Promotes brain and limb/bone growth
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RB protein
Important in cell cycle regulator, causes excessive proliferation in developing retina, leading to a tumour called retinoblastoma. Prevents G1/S progression.
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HPV
Inactivate RB and leads to excessive proliferation
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Retinoblastoma
Cancer of retina, common in young children. mutation of RB1 on chromosome 13. Negative regulator of cell cycle, inactivation of E2F transcription factor.
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RB1 allele
Autosomal dominant with 90% pentrance
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Two-hit model
Both alleles need to be affected
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Mitogens activate receptors
Builds up cdk concentrations which causes phosphorylation of rb, leads to transcription, translation and proliferation.
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Hayflick Limit
Mechanisms behind cellular ageing. Cells can only divide 40-60 times before apoptosis
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Replicative senscence
Cells in permanent non-dividing state
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Telomeres
Short repetitive sequences at the end of chromosomes which are not replicated in cell division.
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Telomerase
Only enzyme capable of ending telomere. High levels of expression in embryos, less in adults. Present as early as unfertilised oocyte
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Asymmetric cell divison
Unequal production of one stem cell and one differentiated cell. Used to expand stem cell pools.
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Co-ordinated division
Links with growth and division
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Hypertrophy
Muscle cells expand in size but not number or expand the extra cellular matrix
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Syncitum
Multinucleated cells that results from multiple cells fusions in uni nuclear cells
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Coenocyte
Multiple nuclear divisions without cytokineses.
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Apoptosis
Programmed cell death. Cells systematically destroys itself. Removes the tissue between digits separating fingers/toes.
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Necrosis
Cells die in response to an acute injury.
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Pruning
Post-mitotic neurons, best connected survive and rest undergo apoptosis.
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