Question

Which of the following statements about DNA repair is correct

during excision repair, an exonuclease is the first enzyme involved in removing a single-stranded segment of DNA from the template strand

none of the answer is correct

during mismatch repair, a methylated guanine in the consensus sequence GATC found on the parent strand activates the Mut complex

the Okazaki fragments synthesized during base excision repair are synthesized in a 3’ -- > 5’ fashion

repair of methylated DNA requires a set of proteins operating with the following order: endonuclease, exonuclease, DNA polymerase I, ligase and demethylase

You work with an E. Coli strain for which -during replication- 1 incorrect nucleotide is incorporated every ~104 added nucleotides. When you further investigate this unusually high error rate you find out that the strain carries a mutated DNA polymerase. Which function of the polymerase is most probably compromised?

Group of answer choices

the 3’ - -> 5’ endonuclease activity

the 5’ - -> 3’ polymerase activity

the 3’ - -> 5’ polymerase activity

the 5’ - -> 3’ endonuclease activity

the 3’ - -> 5’ exonuclease activity

The standard free energy change for the conversion of malate to oxaloacetate is ΔG°′ = 30.0 kJ/mol. If the ratio of NAD+ / NADH ratio is 20, and a typical concentration of malate in mitochondria is 0.22 mM, what is the concentration of oxaloacetate at 20 ^oC, when the reaction is at equilibrium?

16.4 mM

0.02 uM

1.2 mM

4.8 nM

32.8 uM

Answer 1

1)The right answer is DNA repair by methylation follows the order of endonclease,exonuclease,followed by DNA polymerase and DNA ligase after that demthylase is used for the demethylation of the parental DNA.The methylation occurs at adenine and not at guanine position in GATC sequence in the parental strand.Okazaki fragments are not synthesised during repair system.The NER or base excision repair involves the use of endonuclease after usage of specialised uvr proteins for the recognition and binding at the damaged areas of DNA.The right answer is 5)

2)Proofreading activity is mediated by 3-5 exonuclease activity in which the incorporation of wrong nucleotide is corrected.So The right answer is 5).The polymerase incorporate nucleotide in5-3 direction during incorrect nucleotide addition there is 3-5 proofreading