Lecture.20.Fall.2013

Instrinsic it just happens wobble base pairing

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Unformatted text preview: sults in mutation after replication • Nonstandard pairing can occur as a result of the flexibility of DNA structure (“wobble”) • Is this intrinsic or extrinsic? instrinsic, it just happens Wobble base pairing leading to a replication error Insertions and deletions may result from strand slippage tirnucelotide reslts from slippage Unequal crossing over produces insertions and deletions Spontaneous Chemical Changes: Depurination apurinic site will continue each time until it is repaired Deamination can also lead to mutations occurs in low frew, intrinsic Chemically induced mutations mutagen: cause mutation about normal threshold • A number of environmental agents are capable of damaging DNA, including certain chemicals and radiation. • Any environmental agent that significantly increases the rate of mutation above the spontaneous rate is called a mutagen. • The first discovery of a chemical mutagen was made by Charlotte Auerbach. • Auerbach started her career in Berlin, studying the development of mutants in Drosophila. Chemically induced mutations • When the Nazis came into power, she emigrated to Britain and continued her work. • She collaborated with John Robson, a pharmacologist, to study the mutagenic effects of mustard gas, used as a chemical weapon in WWI. • Flies were exposed to the gas in a large chamber and mutagenic affects on the progeny were assayed. • She showed that mustard gas was a powerful mutagen • reduced the viability of gametes and increased the number of mutations seen in the offspring of exposed flies. Base analogs Base analogs are chemicals with structures similar to any of the four standard bases 5-bromouracil: structurally similar to thymine, but base pairs with guanine OR adenine Chemicals may alter DNA bases Oxidative reactions oxyg...
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This document was uploaded on 02/25/2014.

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