45714.1 Point mutationsWild-type genemRNAProteinMissense mutation(e.g., G?C→A?T)Nonsense mutation(e.g., CAA→TAA)Frameshift mutation(e.g., +A)Regulatory regionmutationNWNo mRNANo protein= Mutational siteN = Northern blot(RNA)W = Western blot(protein)= Unpredictable migrationFigure 14-4 Effects of common mutations. The effects of some common types of mutationsat the RNA and protein levels.Mechanisms of point-mutation inductionWhen we examine the array of mutations induced bydifferent mutagens, we see that each mutagen is char-acterized by a distinct mutational specifcity,or “pref-erence,” both for a certain typeof mutation (e.g.,G·C:A · T transitions) and for certain mutationalsites, called hot spots.Such mutational speciFcity wasFrst noted at the rIIlocus of the bacteriophage T4.Mutagens act through at least three different mech-anisms. They can replacea base in the DNA,altera baseso that it speciFcally mispairs with another base, or dam-age
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.