Question

Cancer biology

23. The levels of these proteins fluctuate dramatically as cells progress through the cell cycle. These fluctuations are tightly coordinated with the schedule of advances through the various cell cycle phases. For a particular subtype, extracellular signals, notably those conveyed by growth factors, strongly influence their levels. These proteins are: cdc25-like phosphatases b. Cdk kinases c. Protectins d. Cyclins 24. Which of the following best describes the biochemistry that correlates to one of the cell cycle functions of Rb? 2. Unphosphorylated in GO / Hypophosphorylated at entrance into G1 / Hyperphosphorylated with advance of cells through the R point (pre-S phase) b. Hyperphosphorylated in GO / Hypophosphorylated after entrance into G1/ Hyperphosphorylated with advance of cells through the R point (pre-S phase) c. Unphosphorylated in GO / Hyperphosphorylated after entrance into G1/ Unphosphorylated with advance of cells through the R point (pre-S phase) d. Unphosphorylated in GO / Unphosphorylated after entrance into G1 / Unphosphorylated with advance of cells through the R point (pre-S phase) 25. Unlike most other tumor suppressor genes, deletion of p53 is not embryonically lethal - Which of the following statements is most consistent with what this reveas about its' function? p53 is a somewhat weak tumor suppressor gene. b. p53 is primarily a guardian gene- its' deletion allows for embryogenesis. c. p53 is primarily an executioner-its' deletion allows for embryogenesis. U d . p53 functions as both a guardian and an executioner. balance across both of these functions appears to permit deletion in embryos. 26. What is the primary mechanism through which p53 can be spared from MDM2-directed turnover? a. Phosphorylation of p53. b. Over-expression of the MDM2 gene c. Liberation of MDM2 by deletion of ARF. d. Over-expression of mye. 05

Answer 1

23) CYCLINS -- these are the regulatory proteins which regulates activity of CDK .These CYCLINS undergoes a cycle of synthesis and degradation.

24) c) unphosphorylated in G0/ hyperphosphorylated after entrance into G1/ unphosphorylated with advance of cell through the R point.

25) b) p53 is primarily a gaurdian of genome- it's deletion allow for embryogenesis .because p53 is not required for normal cell division , under normal conditions it is unstable and proteosomal degradation of p53 occur

26) a) phosphorylation of p53 Mdm2 (a ubiquitin ligase )that cause proteosomal degradation of p53 . Phosphorylated p53 doesnot bind with Mdm2 so no proteosomal degradation of p53 occurs