UV light Thymine dimer Sugar phosphate backbone CHa hc H C|CH NO H Thymine dimer
Repair of UV damage: excision repair Exposure to UV light 2. Dimer forms 3. Enzyme nicks Nick Nick strand containing dimer 4. Fragment is released from dna 可L TTITTTITATATTTTTT 5. DNA polymerase fills in the gap 十十十 Ligase 6. Ligase seals repaired strand
Repair of UV damage: excision repair
Defective excision repair causes UV sensitivi
Defective excision repair causes UV sensitivity
Various kinds of mutations
Various kinds of mutations
y Starting sequence G GAGCGTLACCATCCA Type of mutation and effect on base sequence (a) Substitution 1. Transition: Purine for purine, pyrimidine for pyrimidine TCTC G CATA GG AG AIGCIG CCA 2. Transversion: Purine for pyrimidine, pyrimidine for purine TCIACIGCATIGGTIAGGT GCGTALICCAITICCA b)Deletion CGT