Please answer all questions 16. Why do normal fibroblasts maintained at high den

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Please answer all questions
16. Why do normal fibroblasts maintained at high densityin culure become A. Cells arrested by contact inhibition have an increased mutation rade,which leads to cl randfomaticn. B. Cells maintained at high density do not arrest upon contact with other cells C. Cels dividing at high density have a higher motation D. Cells that have acquired transforming mutations are selected for under conditions that anrestcel fwision. n culture become transformed? 17. The tumor promoting effects of phorbol esters are likely due t: A. Suppression of TGF- signals. B. The activation of PKCò. C. The damage to DNA (mutations). D. Elevated levels of diacylglycerol. 8. With the introduction in the early 80s of the mammogram, breast cancer incidence went up, but mortality largely remained unchanged. What this mean? A. False positives B. Early detection does not prevent metaslasis C. The spread of cancer cells occurs earier than previously thought D. All of the above Nerve 3 muscle cell humors are ravely observed becante A. Nerve and muscle cells have very well developed DNA repair mechanisms that limit mutations in these cells B. Nerve and muscle cells are terminally differentiated. C. Nerve and muscle cells have short telomeres that get used up during development. D. Nerve and muscle celis do not express telomerase. E. All of the above n D levels are degraded by the proteasome, which prevents the inhibition of cycin E-CDK2 by cylin D CDK4 20. The transition from the cyclin D-CDK4 checkpoint to the Cyclin E-CDK2 checkpoints is due to: B. Cyclin D-CDK4 suppresses TGF-B signals, which activates cycln E-CDK2 C. Cyclyn D levels increase and bind both p21 and p27, which are requiced for CDK4; and ultimately absots all the p21 and p27, which are inhibitory for cyclin E-CDK2 D. Cyclin E-CDK2 phosphorylates cyclin D, which targets cyclin D for degradation by the proteasome.

Explanation / Answer

16. Cell maintained at hight density do not arrest by contact inhibition

17. Activation of PKC or protein kinase C. They do so by reproducing the actions of DAG, diacylglycerol

18. All of the above

19. They are terminally differentiated. They do not divide anymore.

20. Cyclin D cdk4 suppresses tgf beta which then activates cyclin E. Cyclin tgf beta is a growth signal

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