Please answer all questions 6. Why do norma fbroblasts maintained at ligh densiy
ID: 214245 • Letter: P
Question
Please answer all questions6. Why do norma fbroblasts maintained at ligh densiy in ulture become is arrested by contact inhibition have an increased mutation rate, which leads to celtransformation B. Cells maintained at high density do not arrest upon contact with other celis. C. Cells dividing at high density have a higher mutation D. Cells that have acquired transforming mutations are selected for under conditions that arrestcel diesion 17. The tumor promoting effects of phorbol esters are lkely due to A. Suppression of TGF-B signals B. The activation of PKC8 C. The damage to DNA (mutations). D. Elevated levels of diacylgycerol. 18. With the introduction in the earty 80's 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 metastasis C. The spread of cancer cells occurs earlier than previously thought D. All of the above. 9. What are nerve and muscle cell almost never observed. A. Nerve and muscle cells have very well developed DNA repair mechanisms that limit mutations in these ceils 8. 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 teiomerase E. All of the above. A CycinD levils are degraded by the proteasome, which prevents th i ny o B. Cyclin DCDK4 suppresses TGF- signals, which act ates cyc CO2 pa adt ayats s 20. The transtition from the cyclin D-CDK4 checkpalint to the Cyclin E-CDK2 checkpoints s be b C. Cyclyn D levels increase and bind both p21 and p27, which are which are in CDK4 hibitory for cyclin E-CDK2 ates cyclin D, which targets cyclin D for degradation by the D. Cyclin E-CDK2 phosphorylates cyclin D
Explanation / Answer
16) Answer -B
Cells at high desity stop growing due to contact inhibition and thus undergo trasnformation. Due to high rate of mutations, cells detiorate rapidly and cannot proliferate.
17) Answer - B
Phorbol esters are involved in the activation of PKC or protein kinase C. Protein kinase C are involved in a many cell signalling pathways. Hence prolonged exposure to the chemical can result in the development of tumors.
18) answer - A
Mammography is a technique that has a high rate of fasle positives. almost 10% of the mammograms are false positives.
19) answer - B
Cancer is usually seen in cells that are constantly dividing. As during this porcess mutations can occur that can result in tumor formation.
In adults ,Nerve and muscle cells are completely diffrentiated and do not divide. Hence, it is rare to see tumor formations in these cells.
20) Answer - B
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