Jane has three strains of yeast, which she has labeled X, Y, and Z. Jane knows t
ID: 195515 • Letter: J
Question
Jane has three strains of yeast, which she has labeled X, Y, and Z. Jane knows that one of the strains is wild-type, orte strain is deficient for photolyase only, and one strain is deficient in all systems of DNA repair However, Jane has forgotten which strain is which. She exposes all three strains to increasing doses of UV radiation and records survival. Jane's results are given below 1.00E+00 100E-01 1.00E-02 1.00E-03 1.00E-04 1.00E-05 1.00E-06 1.00E-07 Strain X Strain Y -strain Z 0 20 40 60 80 100 UV Exposure (woules) Which of the following is correct? X is most likely the wild-type strain X is most likely the photolyase-deficient strain X is most likely deficient for all DNA repair systems Y is most likely the wild-type strain Y is most likely the photolyase-deficient strain Y is most likely deficient for all DNA repair systems Z is most likely the wild-type strain Z is most likely the photolyase-deficient strain Z is most ikely deficient for all DNA repair systemsExplanation / Answer
A given yeast cell has many DNA damage repair mechanisms. One of them is photolyases that repair damage caused by exposure to ultraviolet light. Hence, we can arrange the strains in order of most resistance to UV as:
(Most resitant to Least Resitant) : Wild-type >> Photolyase-deficient >> All DNA repair system deficient
Yeast Strain X has an intermediate survival fraction
Yeast Strain Y has the highest survival fraction
Yeast Strain Z has the lowest survival fraction
Comparing the above two sets of information, we can deduce that:
X is most likely the photolyase-deficient strain
Y is most likely the wild-type strain
Z is most likely deficient for all DNA repair systems
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