BIOL 039 Lecture Notes - Lecture 18: Ap Site, Depurination, Tautomer
Document Summary
Spontaneous nucleotide base changes (dna replication errors) Dna nucleotide bases can occasion-ally convert to alternative structures called tautomers. With slight differences in bonding and placement of hydrogen (h) atoms. They are rare and occur transiently in ratio 1:104-105. Rare tautomers are unstable, they quickly revert back to common and more stable form. Tautomeric shifts affect base-pairing (dna replication errors) Tautomeric shifts can lead to base-pair mismatches and incorporation of incorrect bases during replication. This is the most common form of dna replication error. Mutation caused by tautomeric shifts (dna replication errors) Standard nucleotide and base pairing of g/c in parental dna. Tautomeric shift of the common g (keto-form) to the rare g (enol-form) The g-enol tautomer mispairs with the common t (keto-form) Tautomeric shift of g-enol back to g-keto form results in a transition mutation: The second reason for the naturally occurring mutations is the spontaneous nucleotide chemical changes. Two of the most frequent dna lesions result from.
