DNA damage and repair
- 1. Presented By Shouvik Mondal Netaji Subhas Chandra Bose Institute of Pharmacy
- 2. Deoxyribonucleic acid (DNA) is a macromolecule that carries genetic information from generation to generation. It is responsible to preserve the identity of a species over millions of year.
- 3. DNA damage is an alteration in Chemical structure of DNA such as a break in a strand of DNA, a base missing from the back of a DNA, or a chemically changed base. Causes of DNA Damage ļ Radiation ļ Free Radicals ļ Chemicals etc.
- 4. Types of DNA Damage G A CT ds DNA Break C-U deamination AP site Covalent X-linking Thymidine dimer ss Break Mismatch
- 5. Major types of DNA Damage Category Types 1. Single Base Alteration Deamination (C āU, Aā Hypoxanthine) Depurination Base Alkylanation 2. Two Base Alteration UV light induced pyrimidine dimer alteration (T-T) 3. Chain Breaks Oxydative free radical formation 4. Cross Linkage Between bases in the same or opposite strands. Between the DNA and protein molecules.
- 6. Mutation ā¢Transitions ā Purine Purine OR Pyrimidine Pyrimidine is replaced ā¢Transversation ā Purine Pyrimidine OR Pyrimidine Purine is replaced PointMutation ā¢Insertion ā Insert of base ā¢Deletion ā Delete of base Frameshit Mutation
- 7. Mechanism of DNA Repairing 1. ā¢Base Excision Repair 2. ā¢Nucleotide Excision Repair 3. ā¢Mismatch Repair 4. ā¢Double Stand Break Repair
- 8. BASE EXICISION REPAIR The bases Cytosine, adenine and guanine can undergo spontaneous depurination to respectively from Uracil, hypoxanthine and xanthine. These altered bases do not exist in the normal DNA, and therefore need to be removed. This is carried out by base exicision repair.
- 9. NUCLEOTIDE EXCISION REPAIR The DNA damage due to ultraviolet light ionizing radiation and other environmental factors often results in the modification of certain bases, strand breaks, cross linkage, etc. Nucleotide excision repair is ideally suited for such large scale defects in DNA Disease- Xerodrma Pigmentosum
- 10. MISMATCH REPAIR Disease- Hereditary Nonpolyposis Colon Cancer (HNPCC)
- 11. DOUBLE-STRAND BREAK REPAIR ļ Double Strand Breaks in DNA are dangerous. ļ They result in genetic recombination which may lead to chromosomal trans location, broken chromosomes and finally cell death. ļ DSBs can be repaired by homologous recombination or non-homologous end Joining.
- 12. Thank You