1. Which band is LEAST likely to be the result of a nucleotide excision repair p
ID: 209615 • Letter: 1
Question
1. Which band is LEAST likely to be the result of a nucleotide excision repair protein bound to UV132?
A Band W
B Band Y
C Band X
D Band Z
2. Which of the following proteins is most likely to bind first to UV132?
A UvrC
B Helicase
C Glycosylase
D UvrA
E AP endonuclease
Proteins involved would increase leading to impaired cell functions and inheritance of mutations in daughter cells. In humans germline mutations and somatic mutations escaping DNA r cancers, respectively. The experiment described in this test was aimed at identifying DNA repair proteins in monkey and amoeba cells in repairing DNA damage are vital for all cells. Without DNA repair, the rate of mutations repair may lead to inherited diseases and malignant Radioactively labeled dsDNA fragments 132 base pairs in length were prepared and then divided into two aliquots. One radioactive DNA aliquot, labeled 132, was not treated. The other radioactive DNA aliquot was irradiated with UV light, this aliquot was labeled UV132. Aliquots of the 132 fragment (Samples 1-7 in Figure 1) and the UV132 fragment (Samples 8-14) were then incubated alone (Samples 1 and 8), or in the presence of proteins from a monkey cell homogenate (M; Samples 2-4 and 9-11) or in the presence of proteins from an amoeba cell homogenate (A; Samples 5-7 and 12-14). The purpose of adding the protein extracts was to determine if repair proteins that bind to damaged DNA could be detected. Various amounts of a preparation of other (not the same sequence as 132) DNA but unlabelled (not radioactive; "cold") and undamaged, were also added to some of the mixtures (Samples 3, 4, 6, 7, 10, 11 13, 14) with the radioactive DNA. These mixtures of radioactive DNA, proteins, and in some tubes, "cold" DNA, were electrophoresed in a polyacrylamide gel under conditions in which protein binding to DNA was not disrupted (native conditions). Under these conditions of electrophoresis, if a protein is bound to the DNA fragment, then the mobility of the DNA fragment will be shifted (it will move less rapidly through the gel). This technique is called Electrophoretic Mobility Shift Assay (EMSA). With the addition of 10 ng of “cold", there are 100,000x more "cold" DNA fragments than there are radioactive DNA fragments. cold DNA (ng) 0 0 1 10 0 1 10 0 0 1 10 0 1 10 cold" DNA (ng) - M M M A A A cell extract cell extract Band W Band X 8 9 10 11 12 13 14 Figure1 EMSA with radioactive 132 EMSA with radioactive UV132Explanation / Answer
1. Band W is least likely bind to the UV132. 2. Helicase proteins is most likely to bind first to UV132.
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