A DNA template plus primer with the structure 3\'P - TGCGAATTAGCGACAT - P - 5\'

Question

A DNA template plus primer with the structure

3'P - TGCGAATTAGCGACAT - P - 5'
5'-P -ATCGGTACGACGCTTAAC-OH-3'
is placed in an in vitro DNA synthesis system, containing a mutant form of E.coli DNA polymerase I that lacks 5' to 3'exonuclease activity, but has 5' to 3'polymerase and 3' to 5' exonuclease activities.
a. (1pts) What should be present in the in vitro synthesis system for reaction to occur?

b. ( 1 pts) What will be the structure of the final product?

c. (1 pts)What will be the first step in the reaction sequence?

Explanation / Answer

a. Assuming that nucleotides are present in the system, we need a 3'-OH for the other strand too. The enzyme primase should be present to add primers on the 3'-5' strand. ---------------------------------------------- b. The final product would be a single new DNA strand. The DNA would still have the primer as the DNA polymerase lacks the 5'-3' exonuclease activity and cannot remove the primer. ---------------------------------------------- c. The first step in the reaction sequence would be the the recognition of the opposite template and attachment of the complementary base in the new strand.

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