Question

4. Short response (2 sentences max, 6pts each) A. Many yeast species have only one cyclin-dependent kinase (Cdk), which activates protein targets that drive events in multiple phases of the cell cycle. Why doesn't this Cdk activate G1-, S-, G2-, and M-phase proteins all at the same time? B. Please describe how cell death by apoptosis can play a beneficial role in the body's healthy growth. C. For a cell starting in G1, place the following cell cycle events in order A. Actin & myosin act on the contractile ring B. Centrosomes are duplicated C. Condensin is activated D. Ndc80 attaches to spindle microtubules E. S-phase cyclins are expressed START G1 D. How do the proteins integrin and cadherin play a role in the progression of tumors from benign to malignant?

Answer 1

ANS. 4 (A) Because In most of the yeast species only one CDK is present known as cdk28 . It is activated when combined with cyclins proteins . There are different cyclins for each step in cell cycle one being active at a time with the help of other proteins factors . Other times it will not be active as they are either sequestered by inhibitor protein or not at all synthesised .

Ans 4(B) Apoptosis or programmed cell death help in renewal of cells by providing material from those worn out or dead cells which have been disposed by lysosomal enzymes. If Apoptosis is not regulated then it might cause cancer .

ANS. 4(c) E -C-B-D-A is the sequence

ANS . 4 (D) cadherin and integrin proteins help cells attach to each other and to extra cellular matrix . If there is mutation in Gene coding these proteins cell adhesion to each other will be affected and migrability of cell will increase this being shown by cancerous cells which metastasize .