The document discusses non-homologous end joining (NHEJ), a critical DNA repair mechanism for double-stranded breaks caused by ionizing radiation or chemical agents. It details the role of a multi-component protein complex, including the ku protein and dna-pk kinase, in binding broken DNA ends and facilitating repair via mammalian dna ligase-IV. This process ensures genomic integrity by directly repairing double-stranded breaks without the need for homologous sequences.

1. RECOMBINATION ERROR
Or
Double stranded DNA repair
Or
Non-homologous end joining repair
Presented by
Mr.Karthick J.

2. • It is also called double stranded DNA repair
because in this phenomenon repair of the two
broken ends of the DNA takes place and protect
the genome from further degradation .
•Double stranded breaks are generated by
exposure to ionizing radiation or chemical
mutagens or during recombination events .

3. • A multi-component protein complex directs a DNA
Ligase to the break.
• The complex contains a protein called Ku, having two
non – identical subunit binds to two broken ends of
the DNA

4. • The binding of Ku is accomplished by the DNA -PK
Protein kinase.
• It activates a third protein XRCC4, which interacts with
the mammalian DNA Ligase –IV directing this repair
to join the double strands broken ends.
• Like recombination, non-homologous ends are joined
by this process.

5. • Therefore, this type of repair process is also
called non- homologous end joining repair
process.