140-S08-Mar5 - Mutations (changes in DNA): the lifeblood of...

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Mutations (changes in DNA): the lifeblood of genetic analysis hence most mutations with any functional consequence ( mutant phenotype ) disrupt normal ( wildtype ) gene function fact : it’s easier to mess things up than to make them better
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Mutations (changes in DNA): the lifeblood of genetic analysis Geneticists make mutations that disrupt normal gene functions (thereby creating a functional difference between alleles) to discover what genes do what (…and sometimes geneticists can learn a thing or two about “how” even before biochemists enter the picture) …so they can tell biochemists where to look to learn how those genes do what they do
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Mutations (changes in DNA): the lifeblood of genetic analysis Not all mutant phenotypes are equally informative.
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Fig. 20.19 wildtype Krüppel hunchback knirps examples of some maximally informative mutant phenotypes for understanding metazoan pattern formation
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Forward genetics: Reverse genetics: ultimately determine wildtype molecules ultimately determine mutant phenotype (functional consequences of disruption) to infer wildtype function start with mutant phenotype (functional consequences of disruption) to infer wildtype gene function start with wildtype molecules (ultimately transcription units a.k.a. genes) (learn molecular mechanism) (…and learn molecular mechanism)
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Mutations : the lifeblood of genetic analysis …to infer wildtype gene functions Not Mendel’s goal: Not Morgan’s goal: (predict the appearance and breeding behavior of hybrids ) (learn how inherited information is transmitted & how it changes ) (neither had any hope of discovering what gene are )
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“What are the genes? What is the nature of the elements of heredity that Mendel postulated as purely theoretical units? … Frankly, these are questions with which the working geneticist has not much concern himself… T.H. Morgan The Relation of Genetics to Physiology and Medicine Nobel Lecture , June 4, 1934
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Mutations : the lifeblood of genetic analysis Herman Muller ( 1930s ): inferred how mutations can affect gene functioning. Muller Muller : exploited giant polytene chromosomes & invented balancer chromosomes ( functional categories ) ( mutagenesis ) ( ) (Nobel Prize 1946) a Morgan "student": (1) What kinds can we make?
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This note was uploaded on 08/01/2008 for the course MCB 140 taught by Professor Urnov during the Spring '08 term at University of California, Berkeley.

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140-S08-Mar5 - Mutations (changes in DNA): the lifeblood of...

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