11. Put the following events in the correct order. All steps are not shown. I. S
ID: 255673 • Letter: 1
Question
11. Put the following events in the correct order. All steps are not shown. I. S-Cdk phosphorylates Orc. II. Rb is inhibited by Gl-Cdk. III. Mck phosphorylates Erk IV. Myc induces transcription. V. E2F binds to a promoter D. V, Ill, I, II, IV. 12. You have a mutation that causes Myc to be overactive, resulting in increased amounts of cell division. What second mutation would protect these cells? A. Inactivating mutation in Ras. B. Rb that cannot be phosphorylated. C. Overactive mutation in E2F. D. Inactivate Weel kinase. E. Inactivating mutation in Rb.Explanation / Answer
Q.11 Answer is B. correct order is 1. Mek phosphorylates ERK. It migrates to nucleus and acts upon transcription factors which promotes transcription of Fos, jun,Oct, Myc. These again acts as transcrption factors for second level gene expression. e.g cyclin D. so G1 cdk activated and it inhibits RB by phosphorylation ,It induces confirmational change and Rb leaves E2F. E2F having nuclear localization signal(NLS) gets exposed after seperation of Rb. So it enters nucleus and binds to promoter for expression of Cyclic E and Cyclin A. This S cdk phosphorylates Orc and replication is initiated.
Q.12 Answer is B- Rb that cannot be phosphorylated. When Myc is overactive cell division will proceed. But when Rb cannot be phosphorylated then E2F will not be free. Its NLS will not be visible and it will not enter nucleus to bind with promoter of CyclinE & cyclin A. So cell will not proceed to S phase and cell division will be arrested.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.