Question

Which among the following correctly describes the function of the enzyme DNA ligase?

• A. Formation of phosphodiester bonds between DNA fragments
• B. Formation of hydrogen bonds between the two strands of DNA
• C. Formation of phosphodiester bonds between the two strands of DNA
• D. Both a and b

Answer 1

The correct option is A Formation of phosphodiester bonds between DNA fragments

DNA ligase is an enzyme used to catalyze the formation of phosphodiester bonds between deoxyribonucleotides. In rDNA technology, it is used in joining the DNA fragments generated from two different biological sources which have complementary overhangs. This helps in forming a recombinant DNA. DNA ligases are also called ‘molecular glue’ as they help in sealing gaps between DNA fragments.

In double stranded DNA, the two strands are connected by means of hydrogen bond. Adenine binds with thymine by means of two hydrogen bonds while cytosine binds with guanine by means of three hydrogen bonds. DNA ligase is not required for the formation of hydrogen bonds between them.
Phosphodiester bonds are not formed between two strands of DNA.
Therefore, the function of DNA ligase is to form phosphodiester bonds between DNA fragments.