In genetic cloning, the primary function of DNA ligase in recombinant DNA technology is to:

• A. Separate DNA fragments based on size using an electric field in agarose gel
• B. Cut DNA at specific recognition sequences to create sticky or blunt ends
• C. Covalently join DNA fragments by sealing nicks in the sugar-phosphate backbone, forming phosphodiester bonds
• D. Synthesize complementary DNA strands using an RNA template

Answer: (C)

Verified step by step guidance

1. Understand the role of each enzyme or process mentioned in recombinant DNA technology to distinguish their functions.
2. Recall that DNA ligase is an enzyme that facilitates the joining of DNA strands together by catalyzing the formation of phosphodiester bonds between the sugar-phosphate backbones of DNA fragments.
3. Recognize that separating DNA fragments based on size using an electric field in agarose gel is the function of gel electrophoresis, not DNA ligase.
4. Know that cutting DNA at specific recognition sequences to create sticky or blunt ends is the role of restriction endonucleases (restriction enzymes), not DNA ligase.
5. Identify that synthesizing complementary DNA strands using an RNA template is the function of reverse transcriptase, not DNA ligase.