Question

You are characterizing a new DNA polymerase. When the enzyme is incubated with [32P]DNA and no dNTPs, you observe the release of [32P]dNMPs. This release is prevented by adding unlabeled dNTPs. Which of the following describes the reactions that most likely underlie these observations?

a)The DNA polymerase contains 3'-5' and a 5'-3' exonucleases that degrade DNA to produce [32P]dNMPs.

b)The DNA polymerase contains a 5'-3' exonuclease that degrades DNA to produce [32P]dNMPs.

c)The DNA polymerase contains a 3'-5' exonuclease that degrades DNA to produce [32P]dNMPs.

d)Any of the above could explain these observations.

e)None of the above.

Answer 1

Answer:

Option c. The DNA polymerase contains 3'-5' exonuclease that degrades DNA to produce [32P] dNMPs

Explanation: Option a which states that it is a 5'-3' exonuclease is not true, as the addition of dNTPs inhibits 32P dNMP production and do not produce dNMPs as given in option a. So, option a is wrong answer

Option b states that it contains 5'-3' exonuclease which also not correct since, the polymerase extends form 3'-5'. Hence option b is also wrong

Option c is true is true which best explains the reaction by offering protection to the 5' terminus of radioactive DNA.

Since option a and b are false option d and e cannot be true