Depurination Release of adenine or guanine bases.

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Presentation transcript:

Depurination Release of adenine or guanine bases

Deamination Often converts cytosine to uracil

Pyrimidine Dimers Linkage of adjacent pyrimidine bases

Summary Of DNA Damage hydrolysis (including depurinations and deaminations) oxidation methylation

Replication Of Deaminated Cytosine

Replication Of Depurinated Nucleotide

Base Excision Repair Remove damaged base using DNA glycosylase Cut phosphodiester backbone Fill in gap

Damage Detection in Deaminated DNA Bases Deamination leads to unnatural base, removed by DNA glycosylase Exception: Deamination of methylated C at CG dinucleotide generates T that is inefficiently removed Methylated C common site for mutation

Nucleotide Excision Repair Multienzyme complex Recognizes bulky lesion Cuts phosphodiester backbone

Repair of Double Strand Breaks NHEJ: Ligation of broken ends with loss of sequence HR: Undamaged sister chromatid as template

Diseases Of DNA Repair Disease Defective Process Effect Xeroderma pigmentosum Nucleotide excision repair UV sensitivity, skin cancer BRCA-1, BRCA-2 Repair by homologous recombination Breast and ovarian cancer Hereditary nonpolyposis colon cancer Mismatch repair Colon cancer