BIOL 2107 Lecture Notes - Lecture 8: Proflavine, Gene Expression, Reading Frame
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Gene expression: the flow of genetic information from dna via rna to protein. Rna polymerase transcribes dna to produce an rna transcript. Ribosomes translate the mrna se(cid:395)ue(cid:374)(cid:272)e to s(cid:455)(cid:374)thesize a pol(cid:455)peptide. We have 20 amino acids and 61 codons, 3 of which signify stop. A ge(cid:374)e"s (cid:374)u(cid:272)leotide se(cid:395)ue(cid:374)(cid:272)e is (cid:272)olli(cid:374)ea(cid:396) (cid:449)ith the a(cid:373)i(cid:374)o a(cid:272)id se(cid:395)ue(cid:374)(cid:272)e of the e(cid:374)(cid:272)oded pol(cid:455)peptide. Charles yanofsky did experiments to determine the relationship between nucleotides and amino acids. He generated a large number of trp- auxotrophic mutants in e. coli. This mutation cannot grow in the absence of tryptophan. Yanofsky found that changes at the dna level resulted in changes in the amino acids. This provided evidence that codons must contain two or more base pairs. Intragenic recombination: wild-type allele can be produced by crossing two mutant strains with different amino acids at the same position. A similar study involving frameshift mutations showed that codons consist of three nucleotides.