3. What allows chain termination to occur at each base of the template during an

Question

3. What allows chain termination to occur at each base of the template during an automated sequencing reaction?

a. the presence of a relatively low concentration of ddNTPs

b. the presence of a relatively low concentration of dNTPs

c. the presence of a relatively high concentration of ddNTPs

d. the presence of a relatively high concentration of dNTPs

4. In automated fluorescent sequencing, what would happen if the fluorescently labeled ddATP was inadvertently omitted from the reaction?

a. DNA polymerase does not function without equal concentrations of the four nucleotides

b there would be gaps in the sequence where thymines were present in the template DNA strand

c. the sequence would end where the first thymine was encountered on the template DNA strand

d. the sequence would end where the first adenine should be incorporated

Explanation / Answer

3 - in automated sequencing ddNTPs are used with labelled with different color dye these ddNTPs bind to their complementary base. The labelled ddNTPs when bind to their complementary bases chain termination occur. They bind randomly. so when they bounded to their complementary base their concentration is getting down so the correct answer is a. the presence of a relatively low concentration of ddNTPs

4- DNA polymerase function with equal probablity for all bases.ddATP will bind to their complememntary base i.e. thymine so its correct answer is b there would be gaps in the sequence where thymines were present in the template DNA strand

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