Genetic Code - mutation does not occur in the gene As we...

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Genetic Code Suppressor Mutations There is a one other class of mutations, called suppressor mutations. These mutations are "mutations of mutations", which lead to a new type of change in the genetic code. There are two main classes of these mutations. A true reversion mutation occurs when there is a second mutation that restores the natural sequence of the genetic code. For example, a frameshift insertion could be suppressed by a frameshift deletion at a second position in the code. This type of supression is called intragenic suppression because it comes from within the genetic code. The other class of supressor mutation is called extragenic supression because the second
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Unformatted text preview: mutation does not occur in the gene. As we shall see in Translation , transfer RNA (tRNA), plays an important mediating role in the translation of mRNA information into actual proteins. For example, if codon UAC, which normally codes for the amino acid tyrosine, mutates into UAG, a stop codon, the result is a nonsense mutation. But if the tRNA that is specifically designed to "fetch" tyrosine also mutates, so that it now binds with the former stop codon mRNA sequence, then the effect of the two mutations negate each other. This last type of mutation will make a lot more sense after we have more thoroughly discussed tRNA and its function in translation....
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