32. Cell cycle progression is regulated at ensure that all cellular components a

Question

32. Cell cycle progression is regulated at ensure that all cellular components are key transition points, called checkpoints, to present and functioning properly before the cell next stage. Checkpoints are controlled by the level of cyclins. Cyclins are proteins that bind to specific kinases, called cyclin dependent kinases Once activated by cyclins, Cdk proteins phosphorylate specific proteins important for cell cycle progress. Relative amounts of cyclin proteins vary through the cell cycle controlling progression through each stage (Gl, $, G2 and M). D1 Phases of the cell cycle Cyclin DI-Cdk4 regulates entry into S phase through the following signal transduction pathway. Use this pathway to answer the questions below. Part A) Which conditions must be met before the cell can begin DNA replication? Select all that apply. A. The transcription factor, E2F, must be bound to DNA. B. Cyclin D1 must be bound to cyclin dependent kinase (Cdk4). C. Cyclin D1 levels must be high D. Retinoblastoma protein (pRB) must be unphosphorylated. E. Retinoblastoma protein (pRB) must be bound to transcription factor E2F

Explanation / Answer

The correct option is option (A) The transcription factor , E2F, must be bound to DNA.

explanation:-

- Hypophosphorylated RB in Complex with the E2F translation factors binds to DNA , recruit chromatin-remodeling factors and inhibts transcription of genes whose products are required for the S phase of the cell cycle.

- when RB is phosphorylated by the cyckin- D and cycli- E Complexes , it releases E2F. The latter then activates transcription of S-phase genes and causes replication of DNA.

To proceed for DNA replication , E2F must be bound to the DNA.

Hopefully it helps thanks

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