1.5.2 the cell cycle / 1.5.3 control of the cell cycle Flashcards
what does the cell cycle consist of
interphase and mitotic phase
what does interphase involve
- growth and DNA synthesis
- G1 - a growth phase
- S phase - DNA replicated here
- G2 - a further growth phase
what does mitotic phase involve
mitotis and cytokenesis
- in mitotis the chromosomal material is separated by the spindle microtubules
- this is followed by cytokenesis, in which the cytoplasm is separated into two daughter cells
what four phases are there in mitosis
- prophase
- metaphase
- anaphase
- telophase
what occurs in prophase
DNA condenses into chromosomes each consisting of two sister chromatids. nuclear membrane breaks down, spindle microtubules extend from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere region
what occurs during metaphase
chromosomes are aligned at the metaphase plate (equator of the spindle)
what occurs during anaphase
spindle microtubules shorten by depolymerisation, sister chromatids are separated, and the chromosomes are pulled to opposite poles
what occurs during telophase
the chromosomes decondense and nuclear membranes are formed around them
what is progression through the cell cycle controlled by
checkpoints
what do checkpoints control
progression through the cell cycle
what are checkpoints
mechanisms within the cell that assess the condition of the cell during the cell cycle and halt progression to the next phase until certain requirements are met
what are cyclin proteins that accumulate during cell growth involved in
regulating the cell cycle
what do cyclins combine with and activate
cyclin depenent kinases (CDKs)
what are CDKs
cyclin dependent kinases
what does the combination of cyclin proteins with CDKs form
active cyclin CDK complexes
what do the active cyclin CDK complexes phosphorylate
proteins that regulate progression through the cycle
when does progression occur
when sufficient phosphorylation is reached
what occurs at the G1 checkpoint
- retinoblastoma protein acts as a tumour suppressor
- by inhibiting the transcription of genes that code for proteins needed for DNA replication
what does retinoblastoma act as
a tumour suppressor
what inhibits the retinoblastoma protein
phosphorylation by g1-cyclin-cdk
what does the phosphorylation of retinoblastoma protein allow
the transcription of the genes that code for proteins needed for DNA replication
what are the three checkpoints
- G1
- G2
- metaphase
what occurs at the g2 checkpoint
the success of dna replication and any damage to dna is assessed
what does dna damage trigger
the activation of several proteins including p53 that can stimulate dna repair, arrest the cell cycle or cause cell death
what can the activation of proteins such as p53 stimulate
dna repair
arrested cell cycle
cell death
what does the metaphase checkpoint control
progression from metaphase to anaphase
what occurs at the metaphase checkpoint
progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules
what can an uncontrolled reduction in the rate of the cell cycle result in
degenerative diseases
what can an uncontrolled increase in the rate of the cell cycle result in
tumour formation
what is a proto-oncogene
a normal gene usually involved in the control of cell growth or division, which can mutate to form a tumour promoting oncogene
what can a proto-oncogene mutate to form
a tumour promoting oncogene
