primarily G ? C : T ? A transversions. Only the third position of UAG codons would be acted on, resulting in a UAG : UAU change (on the mRNA level), which pro-duces tyrosine. Therefore, if tyrosine were an acceptable amino acid at the corresponding site in the protein, aFatoxin B 1 could revert UAG codons. AFatoxin B 1 would not revert UAA codons, because no G ? C base pairs appear at the corresponding position in the DNA. 2. Explain why mutations induced by acridines in phage T4 or by ICR-191 in bacteria cannot be re-verted by 5-bromouracil. Solution Acridines and ICR-191 induce mutations by deleting or adding one or more base pairs, which results in a frameshift. However, 5-bromouracil induces mutations by causing the substitution of one base for another. This substitution cannot compensate for the frameshift re-sulting from ICR-191 and acridines. 3. A mutant of E. coli is highly resistant to mutagenesis by a variety of agents, including ultraviolet light, aFatoxin B 1 , and benzo(
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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.