Cellcyclle Flashcards
Why is cell division important
– development from a fertilized egg – growth
– repair
Cell cycle
is a series of events that take place in a eukaryotic cell leading to its reproduction.
Result of mitosis
results in two daughter cells with identical genetic information, DNA
Results of meiosis
Meiosisyieldsnonidentical daughter cells that have half as many chromosomes as the parent cell
Events of mitosis
- (prophase)condensation of chromosomes, centromere assemble
-(metaphase)spindle fibre formation and the breakdown of the nuclear membrane
-(metaphase)alignment of chromosomes on spindle equator ,Nuclear membrane disappear
-(anaphase)separation of chromosomes/chromatids
-(telophase)chromosomes de condensed new nuclear membrane form;formation of two new cells
The Mitotic Spindle
• The mitotic spindle is a structure made of microtubules that controls chromosome movement during mitosis
• In animal cells,assembly of spindle micro tubules begins in the centrosome, the microtubule- organizing center
• The centrosome replicates during interphase, forming two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase
Cytokinesis
Process of cytoplasm seperation
Checkpoints in the cell cycle
• The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a clock
• The cell cycle control system is regulated by both internal and external signals
• Theclockhasspecificcheckpointswherethe cell cycle stops until a go-ahead signal is received
Checkpoints in the cell cycle
-entrance into m blocked if dna replication is not completed
-anaphase blocked if chromatids are not properly assembled on mitotic spindle
-dna damage checkpoint: dna replication halted if genome is damaged
-dna damage checkpoint ;entrance into s is blocked if genome is damaged
Cycling
are proteins formed and degraded during each cell cycle.
The cyclins bind to the CDK molecules, therefore regulating the CDK activity and selecting the proteins to be phosphorylated.
Who discovered the start gene and check point
L hart well
Who discovered CDk
P.nurse
Who discovered cyclins
T . Hunt
what phases do cyclins control
➢ G1-phase cyclin- cyclin D and E ➢ S-phase cyclins- cyclin E and A ➢ M-phase cyclin- cyclin B
What phases do cdks control
➢ G1-phase CDK- CDK4/6
➢ S-phase CDK- CDK2
➢ M-phase CDK- CDK1 (CDC2)
What stage do Anaphase-promoting complex (APC, cyclosome) affect
➢ APC triggers the destruction of the cohesins
➢ degrade cyclin B
cyclin-dependent kinases (CDKs)
remain fairly stable in the cell , but each must bind the appropriate cyclin in order to be activated.
Cell cycle inhibitor
Cyclin Kinase Inhibitors (CKI), block the actions of CDKs
Cell cycle and cancer
• Dysregulation of the cell cycle is common during tumorigenesis (cancer display uncontrolled growth)
• Increased levels of CDK molecules and cyclins are sometimes found in human tumours, such breast cancer and brain tumours
• Inhibition of certain CDKs has been shown to inhibit tumour cell growth, induce apoptosis and cause tumour regressions in animal models
• CDKs are potential targets for new anticancer therapy
