28. You are studying DNA polymerase ? (pol ? ) from the bacterium, Bacillus grad

Question

28. You are studying DNA polymerase ? (pol ?) from the bacterium, Bacillus graduatefromUSFilis. Pol ? is exactly like pol III from E. coli, except that activity of pol ? is exactly the same from 5oC to 65oC, a very broad temperature range!

You mix pol ? with dATP, dTTP, dGTP, 2’,3’dideoxy-CTP (called ddCTP*), a short DNA primer with the sequence CCTG, and a source DNA fragment with the sequence, 5’-AATCGTTCACGTTAGCAGG-3’.

You allow the reaction to incubate for 1 hr at 25oC. What is the product of this reaction?

Assume that the concentration of dATP, dTTP, dGTP, and ddCTP* are not limiting.

A. No reaction, because the primer is not complementary to any sequence in the source DNA.

B. CCTGC*

C. CCTGC*TAAC*

D. CCTGC*TAAC*GTGAAC*GATT

E. TTAGC*AAGTGC*AATC*GTCC

Explanation / Answer

Option B is correct.

in the tube dideoxy cytosine nucleotides are added which leads to termination of nucleotides chain synthesis.

In the dideoxynucleotides of DNA 2' position doesn't have oxygen and 3' OH is present which are involved in the formation of phosphodiester bond with the phosphate molecule of another nucleotide.

Dideoxy nucleotide have removal of oxygen at both 2' and 3' that is why known as dideoxynucleotide.

Dueto the abscence of 3' oxygen cytosine nucleotide is not able to make phosphodiester Bond with upcoming nucleotide and chain elongation of DNA terminates at this point.

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