Chapter 15, Problem 2TYK

Which of the following is not a property of DNA polymerase?

a. It adds dNTPs only in the 5' → 3' direction.

b. It requires a primer to work.

c. It is associated with a sliding clamp only on the leading strand.

d. Its exonuclease activity is involved in proofreading.

Summary Introduction

Introduction:

DNA (deoxyribonucleic acid) polymerase is the enzyme responsible for the replication of DNA. The enzymes incorporate the deoxyribonucleotides (dNTPs) into the newly synthesizing DNA molecule from the template DNA. The sliding clamp acts as a processivity promoter factor in the DNA replication. It is crucial for DNA polymerase binding to the template DNA as it prevents the frequent dissociation of the DNA polymerase from the template DNA.

Answer to Problem 2TYK

Correct answer:

The association with the sliding clamp only on the leading strand is not the property of DNA polymerase.

Explanation of Solution

Explanation/Justification for the correct answer:

Option (c) is given as association of DNA polymerase only with sliding clamp on the leading strand. The DNA polymerase is associated with the sliding clamp protein in the leading as well as with the lagging strand. Hence, the Option (c) is correct.

Explanation for incorrect answers:

Option (a) is given as adding of dNTPs only in the $5’\to 3’$ direction. The DNA polymerase adds the dNTPs on the growing end in the $5’\to 3’$ direction. So, it is an incorrect option.

Option (b) is given as primer is needed for DNA polymerase. The primer is an oligonucleotide (short stretch of DNA or RNA [ribonucleic acid]) and is required for the synthesis of DNA using DNA polymerase. So, it is an incorrect option.

Option (d) is given as proofreading is associated with exonuclease activity of DNA polymerase. The enzyme also has an exonuclease activity for proofreading of newly synthesized DNA. These are the property of DNA polymerase. So, it is an incorrect option.

Hence, the options (a), (b), and (d) are incorrect.

Conclusion

DNA polymerase catalyzes the addition of dNTPs in the $5’\to 3’$ direction, it requires a primer for initiation of DNA replication, it has exonuclease proofreading activity, and is associated with sliding clamp on both the leading and lagging strand of DNA.