lecture 9 - Lecture 9 Mechanisms of spontaneous mutation...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 9 Mechanisms of spontaneous mutation and repair
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Mechanisms of spontaneous mutation errors in dna replication transition transversion indels spontaneous lesions/apurinic sites Repair Mismatch repair Base excision repair Nucleotide excision repair Double strand break repair
Background image of page 2
Point mutation : the alteration of a single base pair or a small number of adjacent base pairs. Transition: replacement of a base by the other base of the same chemical category. purine replaces purine (A to G or vice versa) pyrimidine replaces pyrimidine (C to T or vise versa) Indel mutations: insertion or deletion of one or more base pairs. Transversion: replacement of a base of one chemical category by a base of the other. Pyrimidine replaces a purine (C to A or G; T to A or G) Purine replaces a pyrimidine (A to C or T; G to C or T)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Consequences of point mutations within genes Figure 15-2
Background image of page 4
Synonymous: the mutation changes one codon for an amino acid into another codon for the SAME amino acid. Synonymous substitutions never alter the amino acid sequence of a polypeptide chain. Missense or nonsynonomous : the codon for one amino acid is changed into a codon for a DIFFERENT amino acid. The severity of this kind of substitution depends the chemical similarity of the two amino acids in question: highly similar is called conservative versus non-conservative where difference is great affecting characteristics of the protein. Nonsense: the codon for one amino acid is changed into a translation termination codon (STOP)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Transition: replacement of a base by the other base of the same chemical category. Transversion: replacement of a base of one chemical category by a base of the other.
Background image of page 6
Point mutations can alter mRNA splicing Figure 15-3 transition transversion
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Consequences of point mutations on gene products TAA=stop ie: promoter Functional protein? Functional protein?
Background image of page 8
Mechanisms of spontaneous mutations Errors in DNA replication can result from incorrect base insertion during synthesis. Base substitutions may result in transition or transversion. Transitions can result when tautomers (imino and enol) of the normal (keto) form of a given base occur in DNA leading to mismatched pairing of bases…hydrogen bonding characteristics are modified such that C and A will pair or G and T will pair Tautomers : isomers of a molecule such as DNA bases that differ in the positions of the atoms and bonds between them
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 30

lecture 9 - Lecture 9 Mechanisms of spontaneous mutation...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online