0. The DNA fragment given in the figure below is double stranded at each end but
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0. The DNA fragment given in the figure below is double stranded at each end but one of the strand in single stranded in the middle. The polarity of the top strand is indicated (6) How do you expect this gap to be filled in by DNA repair process inside a cell? Which enzymes will be used and mention their role n this process many pieces will the bottom strand have if the gap is filled in the test tube reaction containing only dNTPs and a DNA extension enzyme? It is a known fact that DNA synthesis occurs from 5' to 3'. Please explain with details why the reverse is not possible. . 3Explanation / Answer
1) this may be a case of nucleotide excision repair in which DNA pol 1 plays an important role to fill the gap and nick is sealed by DNA ligase enzyme. DNA pol 1 adding the nucleotide in the gap.
2) the bottom strand have two pieces because there is no DNA ligase enzyme is available to seal the nick between last two nucleotides.
3) this is because of the specificity of the DNA polymerase enzyme which recognizes only 3' OH group and 5' PO4 grout and makes phosphodiester bond.
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