Jilal ak u .x ? ) JH O?JJ1 .x ? Fiverr/m051151 ashLine Login RJ Cell cycle Cance

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Jilal ak u .x ? ) JH O?JJ1 .x ? Fiverr/m051151 ashLine Login RJ Cell cycle Cance x, D BSCI-Konica-201 × ? Q Practice Questio Mohammad x C Secure https://learn.kent.edu/bbcswebdav/pid-8171304-dt-content-rid-99301043_Tcourses/11331-11342-22012-22032.201810Problem%20set%20%20Ch%20.-Q ? 1 Progression through the cell cycle requires a cyclin to bind to a Cdk because (a) the cyclins are the molecules with the enzymatic activity in the complex (b) the binding of a cyclin to Cdk is required for Cdk enzymatic activity (c) cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle (d without cyclin binding, a cell-cycle checkpoint will be activated. 2. The concentration of mitotic cyclin (M cyclin) (a) rises markedly during S phase. (b s activated by phosphorylation. (c) falls toward the end of M phase as a result of ubiquitylation and degradation. (d) s highest in G phase. 3. e G DNA damage checkpoint (a) causes cells to proceed through S phase more quickly. (b) involves the degradation of p53 (c) is activated by errors caused during DNA replication (d) involves the inhibition of cyclin-Cdk complexes by p21 At the end of DNA replication, the sister chromatids are held together by the (a) kinetochores. (c) cohesins. 4. securins. (d istones. 5. The complex (APC) (a) Phosphorylates M cyclin leading to its degradation. (b Ubiquitylates M cyclin leading to its degradation. (c) Is continuously active throughout the cell cycle (d) Is stimulated by S-Cdk

Explanation / Answer

1. Option - B

Reason- The cyclin dependent kinases (cdk) has a inactive catalytic subunit of protein kinase which can be activated only by binding of a regulatory protein called cyclin. After the activation of cdk it helps in crossing the cell cycle check Point by phosphorylation.

2. Option - C

Reason - After progression through the cell cycle check Point the cyclin gets degraded which results in the inactivation of the cdk. Thus the level of M cyclin gets reduced at the end of M phase.

3. Option - D

Reason - P21 is the most common cdk inhibitor which is usually involved in the inhibition of cyclin - cdk complex during recognition of DNA damage and arrest the cell cycle at G1 phase.

4. Option - C

Reason - At S phase after the replication of DNA the sister chromatids are held together by cohesion with the help of chromatid associated cohesion protein. These gets degraded when the cell enters the mitotic phase.

5. Option - B

Reason - The anaphase promoting complex helps in the degradation of M cyclin by ubiquitination process . Thus it helps the cell to enter cytokinesis.

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