The single-stranded ends of DNA molecules can be joined together by:

• A. Restriction Endonucleases.
• B. DNA ligase.
• C. DNA polymerase.
• D. Helicase.
• E. Primase.

Answer: (B)

Verified step by step guidance

1. Understand the role of each enzyme listed in the options: Restriction Endonucleases, DNA ligase, DNA polymerase, Helicase, and Primase.
2. Restriction Endonucleases are enzymes that cut DNA at specific sequences, creating single-stranded ends, but they do not join DNA strands.
3. DNA ligase is an enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond, which is essential for joining single-stranded ends of DNA molecules.
4. DNA polymerase is primarily involved in DNA synthesis, adding nucleotides to a growing DNA strand, but it does not join single-stranded ends.
5. Helicase unwinds the DNA double helix, and Primase synthesizes RNA primers; neither of these enzymes is involved in joining single-stranded DNA ends.