Lecture 9 - cell cycle control Flashcards
what check happens at the G1 checkpoint?
the cell needs to check if it needs to reproduce right now. If yes, it will continue into the S phase of the cycle. If not, it will migrate into the G0 phase and not proceed with cell division.
what check happens at the G2 checkpoint?
the cell checks to see if there are any errors in the replication process of s phase. So is the DNA damaged? is there enough of it? etc.
what check happens at the M checkpoint?
the cell checks to see if all the chromosomes are attached to the mitotic spindles correctly, so when the cell divides, each daughter cell gets have the genetic material.
what are the proteins needed to regulate cell division?
> a regulatory subunit called cyclin
a catalytic subunit with kinase activity which phosphorylates other proteins when bound to cyclin: cyclin-dependent kinase (CDK)
when cyclin binds to Cdk, the protein complex is formed and activated - and this is called the Maturation- promoting factor (MPF)
when does cyclin produce begin?
during s phase
when does cyclin accumulate?
it accumulates during S and G2 phases
what happens towards the end of G2 phase in regards to cyclin?
it builds up to a critical level, that then allows it to bind to the Cdk, forming MPF
what happens in M phase in regards to the regulatory proteins?
MPF accumulation activates mitosis by allowing the cell to bypass and go over the m checkpoint.
what happens in M phase in regards to the regulatory proteins?
MPF accumulation activates mitosis by allowing the cell to bypass and go over the m checkpoint.
what happens to the protein complexes once mitosis is complete?
> MPF is broken down.
Cdk is recycled in the cell
cyclin is broken down
what pushes the cell past the G2 checkpoint?
the high concentration of Cdk-cyclin complexes
what is the result of uncontrolled proliferation of cells?
CANCER!! one or more of the checkpoints don’t work properly
what are the specific genomic causes of cancer?
> if the genes that promote cell divison (oncogenes) are not turned off at the right times, this can lead to cancer.(lesser factor)
if genes that normally inhibit cell division from happening all the time, (tumour suppressor genes) stop working, this can also lead to cancer.
i.e., need tumour suppressor genes all the time, but only need Oncogenes to start transcription.
what is the most frequently mutated gene leading to cancer?
p53.
> a tumour supressing gene.
>in normal DNA, p53 does not attach to gene and cells replicate normally.
> in mutated, damaged DNA, p53 causes production of proteins that prevent initiation of the cell cycle, therefore, no replication of cells with damaged DNA
what is the most frequently mutated gene leading to cancer?
p53.
> a tumour supressing gene.
>in normal DNA, p53 does not attach to gene and cells replicate normally.
> in mutated, damaged DNA, p53 causes production of proteins that prevent initiation of the cell cycle, therefore, no replication of cells with damaged DNA
