Stem cells and cell cycle Wk 4 Flashcards
Describe and outline the cell cycle
G0: resting/stationery phase G1: Cell Growth S: DNA replication G2: Preparation M: Mitosis and cytokenisis
Describe an overview of cell division and the generation of new cells.
Stem cell -> dividing precursor cells -> terminally differentiated cells.
What does mitosis and cytokenisis mean?
Mitosis: Nuclear division
Cytokenisis: Cytoplasmic division
Describe an overview of the role of gene expression in determining cell phenotype and the process of cell differentiation.
Tissue-specific transcription factors (regulatory proteins) determine how each cell differentiates.
Transcription factors can alter gene expression by changing histone acetylation, and also DNA methylation patterns.
What does terminally differentiated?
When a cell is determined for a function and cannot re-enter the cell cycle unless in a lab.
Describe and outline the importance of check points and control mechanisms.
Cell cycle stages avoid out of control proliferation (cancer).
Check points avoid this.
G1: Is environment favourable (does the cell have enough resources). Checks if the cell is ready for S phase.
G2: Is DNA replicated and repaired correctly before mitosis? If there is damage, it is held for repair.
Mitosis: End of mitosis. Checks alignment of chromosomes to spindle before cytokenisis.
Describe and outline the importance of check points
Cell cycle stages avoid out of control proliferation (cancer).
Check points avoid this.
G1: Is environment favourable (does the cell have enough resources). Checks if the cell is ready for S phase.
G2: Is DNA replicated and repaired correctly before mitosis? If there is damage, it is held for repair.
Mitosis: End of mitosis. Checks alignment of chromosomes to spindle before cytokenisis.
Describe and outline the importance of control mechanisms.
Cyclin and cyclin-dependent protein kinsases concentration rises during mitosis and falls in interphase.
Cdk add phosphates to target proteins only in presence of cyclin; thus different levels of cyclin changes the cycling-dependent kinase activity during the cell cycle.
Cdk active when cyclin autophosphorylates itself before phosphorylating other proteins which triggers the stages of the cell cycle.
Cyclin levels are degraded during proteasomal degradation.
Proteasome is a large complex of proteins which binds to cyclin and degrades / chops it up into amino acid blocks.
Proteasome is controlled by the small modifier ubiquitin. Poly-ubiquitin is a tagged protein, marking cyclin as “ready for degradation” by proteasome.
Describe and outline the importance of control mechanisms.
Cyclin and cyclin-dependent protein kinsases concentration rises during mitosis and falls in interphase.
Cdk add phosphates to target proteins only in presence of cyclin; thus different levels of cyclin changes the cycling-dependent kinase activity during the cell cycle.
Cdk active when cyclin autophosphorylates itself before phosphorylating other proteins which triggers the stages of the cell cycle.
Cyclin levels are degraded during proteasomal degradation.
Proteasome is a large complex of proteins which binds to cyclin and degrades / chops it up into amino acid blocks.
Proteasome is controlled by the small modifier ubiquitin. Poly-ubiquitin is a tagged protein, marking cyclin as “ready for degradation” by proteasome.
Ubiquitylation by enzymes under the control of growth factors.
Cdk is unable to phosphorolyate proteins once deactivated by proteasome.
Describe and outline the importance of control mechanisms.
Cyclin and cyclin-dependent protein kinsases concentration rises during mitosis and falls in interphase.
Cdk add phosphates to target proteins only in presence of cyclin; thus different levels of cyclin changes the cycling-dependent kinase activity during the cell cycle.
Cdk becomes active when cyclin autophosphorylates itself before phosphorylating other proteins which triggers the stages of the cell cycle.
How is cyclin degraded?
Cyclin levels are degraded during proteasomal degradation.
Proteasome is a large complex of proteins which binds to cyclin and degrades / chops it up into amino acid blocks.
What controls proteasomal degradation?
Proteasome is controlled by the small modifier ubiquitin. Poly-ubiquitin is a tagged protein, marking cyclin as “ready for degradation” by proteasome.
What is the functional consequence of ubiquitylation?
Cdk is unable to phosphorolyate proteins once deactivated by proteasome (Ubiquitylation).
What controls ubiquitylation?
Ubiquitylation by enzymes under the control of growth factors.
What is the control protein retinoblastoma (Rb) protein?
Controls S phase entry (G1 check point).
What is E2F?
A transcription factor that activates transcription of genes / components required for S-phase transition.
