CONTENT INTRODUCTION OF DNA REPAIR WHY DOES DNA REPAIR REQUIRED? TYPES OF DNA REPAIR MECHANISM OF DNA REPAIR APPLICATION OF DNA REPAIR CONCLUSION INTRODUCTION DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. The DNA repair ability of a cell is vital to the integrity of its genome and thus to the normal functionality of that organism. A failure to repair DNA produces a mutation.

1. ST. ALOYSIUS COLLEGE
JABALPUR
M.SC SECOND SEMESTER DEPARTMENT OF
BIOTACHNOLOGY

2. PRESENTED BY

3. CONTENT
• INTRODUCTION OF DNA REPAIR
• WHY DOES DNA REPAIR REQUIRED?
• TYPES OF DNA REPAIR
• MECHANISM OF DNA REPAIR
• APPLICATION OF DNA REPAIR
• CONCLUSION

4. INTRODUCTION OF DNA REPAIR
• DNA repair is a collection of processes by which a cell identifies
and corrects damage to the DNA molecules that encode
its genome.
• The DNA repair ability of a cell is vital to the integrity of its genome
and thus to the normal functionality of that organism.
• A failure to repair DNA produces a mutation.

5. WHY DOES DNA REPAIR IS REQUIRED ?
• DNA damage is an alteration in the chemical structure of DNA.

6. TYPES OF DNA REPAIR
TYPES OF
DNA REPAIR
DIRECT
REVERSAL
SINGLE STRAND
DAMAGE
DOUBLE STRAND
BREAKS
 Photoreactivation
 Methyl group removal
 BER
 NER
 MMR
 Non-homologous end joining (NHEJ)
 Microhomology-mediated end joining (MMEJ)
 Homologous recombination

7. DIRECT REVERSAL PHOTOREACTIVATION

8. DIRECT REVERSAL METHYL GROUP REMOVAL

9. EXCISION REPAIR- BER
A. RECOGNIZATION AND REMOVAL OF
UNWANTED BASE.
B. UNWANTED BASE ARE :-
• URACIL
• HYPOXNTHINE
• XNTHINE
• 5 METHYLE GUANINE
• 3 METHYLE ADENINE
C. ENZYME INVOLVED IN BER
• GLYCOSYLASE
• AP ENDONEUCLEASE
• DNA POLYMERASE
• DNA LIGASE

10. EXCISION REPAIR- NER
A. RECOGNIZATION AND REMOVAL OF
DIMERS AND DNA LESIONS.
B. CAN VARITY OF BULKY LESIONS :-
• PYRAMEDINE DIMERS
• CHEMICALY MODIFIED BASES
C. ENZYME INVOLVED IN NER
• Uvr A
• Uvr B
• Uvr C ( EXCINUCLEASE ACTIVITY )
• Uvr D ( HELICASE )
• DNA POLYMERASE
• DNA LIGASE

11. EXCISION REPAIR- mdMMR
A. RECOGNIZATION AND REPAIR OF MISMATCH
BASES OR MISINCORPORATED BASES OR
SMALL INSERSION- DELETION LOOP.
B. PROBLEM :- DIFFERANTIATION BETWEEN TEMPLATE AND
NEWLY SYNTHESISED STRAND.
SOLUTION :- METHYLATION OCCURE AT N OF ADENINE
IN GATC SEQUENCE.
C. METHYL DIRECTED MISMATCH REPAIR IS STRAND SPECIFIC.
DURING DNA SYNTHESIS THE NEWLY SYNTHESISD STRAND
WILL COMMONLY INCLUDED ERRORS.
6

12. 1. MUT S
2. MUT L
3. MUT H
4. DNA POLYMERASE
5. DNA LIGASA

13. DISEASE CAUSED BY INFFECTIVE DNA REPAIR
XERODERMA PIGMESTOSUM
 MULTIPLE SKIN CANCERS
 DECREASED ABILITY TO REPAIR DNA DAMAGED BY UV LIGHT
 INCREASED SUSCEPTIBILITY TO MEANOMA
CONGENITAL NEVI
 PRESENT AT BIRTH
 THOSE GREATER THEN 20MM HAVE A 5-10% CHANCE OF DEVELOPING MEANOMA

14. XERODERMA PIGMENTOSUM
• Xeroderma Pigmentosum (XP) is a rare
genetic disorder that occurs worldwide in all
races and ethnic groups.
• First described by Hebra and Kaposi in 1874
the disorder is characterised by marked
photosensitivity and premature onset of all
major types of skin cancer.
• It is characterised by inability of a cell to repair damage caused by UV leading to genetic
instability and skin cancer

15. XERODERMA PIGMENTOSUM PATHOPHYSIOLOGY
NUCLEOTIDE EXCISION REPAIR PATHWAY