7. What is the purpose of cell-cycle checkpoints, such as the DNA-damage checkpo

Question

7. What is the purpose of cell-cycle checkpoints, such as the DNA-damage checkpoint or the spindle-attachment checkpoint?

B. You isolate mutant cells defective in the DNA-damage checkpoint, but you find that under normal laboratory conditions, the mutant cells grow and divide at the same rate as wild-type cells. Why doesn’t the defect in the DNA-damage checkpoint have a large effect on cell growth and division rates under normal conditions?

C. Please describe an experimental condition in which wild-type cells and mutant cells defective in the DNA-damage checkpoint would show a difference in cell growth and division rates.

D. How would this condition affect the cell growth and division rates in the wild-type and mutant strains from Part 7B?

Explanation / Answer

A Check point stage in eukaryotic cycle which ensure cell divison happened properly.The aim of the check point is to distribute complete and accurate replicas of the genome to daughter cells.In this stage the cell examine both the inernal and external cues to decide whether the cell go through the divison or not.When the check point detect the problem with the DNA or DNA damages that have to be repaired,the cell cycle is halted and cell first complete the DNA replication or repaires the damaged DNA.

There are a three checkpoints,

B ans-DNA-damage checkpoint happends in G-2 checkpoint.Cell enter mitosis before repairing,check point dont have a great affect on cell divison .after this checkpoint If the damage is irreparable, the cell may undergo apoptosis, or programmed cell death after cell divison.

C ans-Schizosaccharomyces pombe belongs from the Schizosaccharomycetaceae family and saccharomyces cerevisiae (yeast). if we analysed mutant in both species When DNA is damaged or DNA synthesis is blocked, cells activate checkpoint pathways they both have a number of proteins that are involved in DNA replication process.It affect replication by depletion of dNTP',(di culeotide tri phosphate).

D-ans-In DNA danage check point Chek -1 or check point kinase 1 and Atr-1 both play a main role if they are fail or lack functioning which may leads to production of genotoxic in the cell .

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