3. (12 points) You are a scientist interested in studying the cell cycle in a ma

Question

3. (12 points) You are a scientist interested in studying the cell cycle in a mammalian system. You start by isolating primary fibroblast cells from mice. Primary cells from wild-type mice tend to accumulate DNA mutations resulting in senescence fairly quickly and don't grow well in vitro, so you isolate these cells from mice with a p53 mutation instead A) What type of cell cycle regulation is affected by p53, and why would a p53 mutation allow the cells to grow better in vitro? Using this p53-mutant fibroblast cell line, you generate several different reporter lines where each expresses one cyclin tagged with GFP (green fluorescent protein) at normal levels. Unfortunately, the labels have fallen off of two of your reporter cell lines: the one with G1/S-cyclin GFP and the one with S-cyclin-GFP. To figure out which one is which, you examine the DNA content of GFP+ cells from each line, and see the following DNA stant Line A Line B B) Which line is which? Explain your answer You use the G1/S-cyclin reporter line to study the function of a new cell cycle inhibitor, drug X. When you add drug X to your cells, none of the cells fluoresce. You examine Cyclin D (the G1 cyclin) and phospho-Rb protein levels by Western blot in these cells and observe the following: untreated Orug X C) At what stage of the cell cycle do cells treated with phospho Rb Drug X arrest? What is this drug's likely target? Explain your answers CyclinD

Explanation / Answer

a) G1/ S checkpoint is affected by p53. Because normally if there is a damage in DNA, p53 arrest cell cycle at the G1/S transition. But if p53 is mutated it cannot prevent in that transition, the cell cycle proceed instead.

b) Line A – G1/S cyclin GFP

Because in G1 stage, there is only one DNA is present.

Line B – S-cyclin-GFP

Because in S phase DNA is replicated and there are two DNA are present.

c) At the G1 to S phase of the cell cycle, cells treated with drug X arrest.

This drug likely target phospho-rb protein. Because if phospho-rb protein is mutated it will never arrest cell cycle. Instead, drug X arrest cell cycle at the G1-S transition.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.