Chapter 22, Problem 1A

Summary Introduction

Introduction:

DNA replication is a process involves the making of identical copy of a DNA from the original DNA molecule. The replication involves 3 steps; initiation, elongation, and termination. Replication takes place in the nucleus of every cell with the help of types of enzymes, topisomerase for relieving the coiling of DNA, helicase for unwinding the helical structure of DNA, primase for primer synthesis, DNA polymerase for synthesizing new DNA fragments, and ligases joins the okazaki fragments on lagging strand of synthesizing DNA.

Answer to Problem 1A

Correct answer:

Deoxyribonucleotides are the building blocks of DNA; DNA polymerase is the enzyme that adds the nucleotides to the growing chain of DNA fragment. Therefore, option (c) is correct.

Explanation of Solution

Reason for correct statement:

Replication involves making of 2 copy of DNA from a single molecule of DNA. Polymerase is the enzyme responsible for polymerizing the deoxyribonucleotides to elongate the growing chain of DNA.

Option (c) is given as “DNA polymerase”.

As, “DNA polymerase is responsible for forming new copies of DNA by adding nucleotides and chemically connecting them to the growing chains of DNA molecule,” it is the right answer”.

Hence, option (c) is correct.

Reasons for incorrect statements:

Option (a) is given as “helicase”.
Helicase is responsible for opening the double helical structure of DNA for the process of replication. So, it is a wrong answer.

Option (b) is given as “RNA polymerase”.
RNA polymerase builds the primer for DNA polymerase that adds nucleotides during elongation. So, it is a wrong answer.

Option (d) is given as “DNA ligase”.
DNA ligase adds the phosphodiaster bonds, to join the Okazaki fragments on lagging strands and also helps in DNA repairing. So, it is a wrong answer.

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

Conclusion

DNA polymerase is responsible for adding new nucleotides to a growing DNA chain during DNA replication.