Chapter 9, Problem 1TQ

Summary Introduction

The DNA replication process begins at the origin of replication site in the genome. The biological process of producing two similar replicas of DNA from single original molecule of DNA is called as DNA replication. The process of DNA replication is the basis for the biological inheritance and it occurs in whole living organisms.

Answer to Problem 1TQ

The DNA replication results in two DNA molecules, each of which has one old strand and one new strand.

Therefore, option (c) is correct. 

Explanation of Solution

Justify the reasons for the correct statement:

The DNA consist of a double helix structure with complementary strands. These complementary strands are separated during the replication. Then, each of the original molecules of DNA serves as a template for the generation of its counterpart. This process is termed as a semiconservative replication. As a result, the new helix will be formed from the original strand of DNA.

Option (c) is given as, “two DNA molecules, each of which has one old strand and one new strand”.

Hence, the option (c) is correct.

Justify the reasons for the incorrect statements:

Option (a) is given as, “two DNA molecules - one with two old strands, and one with two new strands”. 

The DNA replication does not result in two old strands and two new strands. It results in two molecules of DNA with one old strand and one new strand. Hence, it is a wrong answer.

Option (b) is given as, “two DNA molecules, each of which has two new strands”.   

The replication of DNA does not result in two new strands, but it contains one old strand and one new strand. Hence, it is a wrong answer.

Option (d) is given as, “none of the above”

The replication of the DNA results in two molecules of DNA, which has one new strand and one old strand. Thus, the given statement none of the above is inaccurate. Hence, it is a wrong answer.

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

Conclusion

The DNA replication is similar to all biological polymerization process. It continues by coordinated steps and they are catalyzed enzymatically. Thus, the replication of DNA results in the two molecules of DNA and each has one new strand and one old strand.