Question

Compare and contrast non-homologous end joining and homologous recombination. What are the pros and cons of each?

Answer 1

Ans) Pros of Non-homologous end joining is that it is the emergency solution for the double stranded break repair.

Cons of Non-homologous end joining is that it is more error prone.

Pros of Homologous recombination is that it is more accurate (since the exchange of homologous segments occurs).

Cons is it predominates only in S and G2 phases and not in G0 and G1 phase.

Both Homologous recombination and Non-homologous end joining can be used for Double stranded break repair.Both of then can cause gene conversion due replacement of one allele by another by recombination during meiosis.

Homologous recombination is initiated by Rec BCD enzyme (exonuclease V with both nuclease and helicase activity) and it provides 3' DNA. RecA protein assemble on 3' DNA more efficiently. Next process is then strand invasion followed by branch migration and finally the resolution of holliday junction.

Non-homologous end joining is initiated by Ku 70 and Ku 80 heterodimer which recruit DNA dependent protein kinase and Artemis. Artemis has both exonuclease and endonuclease activity. DNA dependent protein kinase activate XRCC4 which bind to DNA ligase and repair the Double stranded DNA break.