DNA REPAIR MECHANISM

BHARATESHA.S 7TH SEM 2014-15GUIDED BY:

CHANDRAKANTH.RMOLECULAR BIOLOGY DEPT.

CONTENTS

• Introduction• Mismatch repair• Base excision repair• Nucleotide excision repair • Transcription coupled DNA repair • Double Strand Break repair• Photo reactivation • Conclusion• References• Acknowledgement

INTRODUCTION

Mismatch repair removes errors that escape proofreading

★Increase the accuracy of DNA by an additional 2-3 orders of magnitude

★Two challenges: ● Scan the genome rapidly● Correct the mismatch accurately ( that is it must recognize the newly synthesized strand)

MutS scans the DNA,recognizing the mismatch from the distortion they cause in the DNA backbone

Base excision repair enzymes remove damaged bases by a base-flipping mechanism

Nucleotide excision repair enzymes cleave damaged DNA on either side of the lesion

Transcription coupled DNA repair Nucleotide excision repair system is capable of

rescuing RNA polymerase that has been arrested by the presence of lesions in the DNA template

Double Strand Break repair model for homologous recombination

Photo reactivation (the enzyme DNA photolyase captures energy from light )

Conclusion

REFERENCES

I. James D.Watson, (2013) Molecular biology of the gene 7th edition, Cold Spring Harbour Laboratory Press, New york- 313-324pp.

II. David L.Nelson, Michael M.Cox, (2011) Principles of Biochemistry 5th edition , W.H.Freeman and Company, New york- 993-999pp.

ACKNOWLEDGEMENT

I would like to thank my guide Chandrakanth.R for his valuable guidance and our course coordinator Dr.N.S.Devaki madam for providing me this opportunity.

THANK YOU