Of the following mutations, which are likely to cause cell-cycle arrest? If you
ID: 186206 • Letter: O
Question
Of the following mutations, which are likely to cause cell-cycle arrest? If you predict a cell-cycle arrest, indicate whether the cell will arrest in G1, S, G2, or M. Explain your answers for all situations presented (14 points) A. a mutation that destroyed the kinase activity of S-Cdk B. a mutation that allowed G1-Cdk to be active independently of its phosphorylation status C. a mutation that removed the phosphorylation sites on the Rb protein D. a mutation that inhibited the activity of Rb E. a mutation that destroys the activity of APCExplanation / Answer
A.a mutation that destroyed the kinase activity of S-Cdk:Cell cycle will be arrested at G1 phase.This is because S-CDK catalyzes phosphorylation of the proteins that are are reqired for initiation of DNA replication in S phase and when its activity is destroyed via mutation,cell cycle will be arrested at G1.
B.a mutation that allowed G1-Cdk to be active independently of its phosphorylation status: No cell cycle arrest will occur and cell will move to S phase and thus cell cycle will continue.
C.a mutation that removed the phosphorylation sites on the Rb: Cell cycle will arrest at G1.Rb is active in its dephosphorylayed form and inactive in its phosphorylated form.In active form,Rb restricts replication of DNA by as it prevents cell cycle progression from from the G1 to S phase of the cell division cycle.When phosphorylated sites are removed by mutation ,RB will fail to be phosphorylated and hence remain active.
D:a mutation that inhibited the activity of Rb :No cell cycle arrest and cell would divide continuosly.
E.a mutation that destroys the activity of APC: The cell cycle arrest will take place in M phase.APC main function is to allow the transition from metaphase to anaphase stage during M phase of cell cycle and when mutated, cell will be arrested in metaphase stage.
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