Question

9. What closes the final nicks in the sugar-phosphate backbone to generate coding and signal joints?

A. TdT
B. Artemis
C. RAG-1/2
D. XRCC4 with DNA ligase IV
E. Ku 70 and Ku 80

Answer 1

Option D). The final nicks in the sugar-phosphate backbone to generate coding and signal joints are closed by DNA ligase IV with XRCC4.

Step-by-step explanation:

DNA ligase IV uses XRCC4 to close the last nicks in the sugar-phosphate backbone that produce coding and signal joints. The creation of a covalent phosphodiester linkage between the 3'-OH end of one DNA fragment and the 5' phosphate end of another DNA fragment is catalyzed by the enzyme DNA ligase IV. A protein called XRCC4 aids in maintaining the complex that DNA ligase IV forms at the nick site. Hence, Option D) is the correct answer.