Question

Deamination of a cytosine base in DNA results in a uracil base, which is disallowed in DNA. To resolve this conflict, this DNA needs to be repaired. For this, the modified base is recognized and removed by a ______, resulting in an AP site, which is recognized and cleaved by an endonuclease for nick-translation.

Select one:

a. exonuclease

b. Uracyl DNA-glycosylase

c. HindIII restriction endonuclease

d. Klenow fragment

e. AP-site endonuclease

Answer 1

Answer: b. Uracyl DNA-glycosylase

The Uracyl DNA-glycosylase is an enzyme involved in base exicision repair system of a cell to prevent mutagenesis caused by deamination of cytosine into uracil. The enzyme hydrolyzes the N-glycosyl bong between the Uracil and the deoxyribose sugar, thereby creating an AP site.

Exonuclease remove entire nucleotides from the ends of the DNA.

HindIII is a restriction endonuclease that makes cuts within both the strands of a dsDNA by recognizing a specific recognition sequence.

Klenow fragment is formed after the digestion of DNA Polymerase I with the subtilisin enzyme.

AP-site endonuclease breaks phosphodiester bonds in the phosphodiester backbone of DNA at the AP-site.

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