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Unformatted text preview: 1. silent mutations do not alter the amino acid specified 2. missense mutations replace one amino acid with another 3. nonsense mutations introduce a STOP codon 4. frameshift mutations result from the insertion or deletion of nucleotides within the coding sequence B. Mutations in a gene outside the coding sequence can also alter gene expression C. Mutations in genes encoding the molecules that implement expression may effect transcription, mRNA splicing, or translation 1. mutations altering genes encoding proteins or RNAs involved in gene expression are usually lethal 2. mutations in tRNA genes can suppress mutations in proteincoding genes The triplet codon represents each amino acid 0 20 amino acids encoded for by 4 nucleotides By deduction:
1 nucleotide/amino acid = 41 = 4 combinations. 2 nucleotides/amino acid = 42 = 16 combinations. 3 nucleotides/amino acid = 43 = 64 combinations. Must be at least triplet combinations that code for amino acids The Genetic Code: 61 triplet codons represent 020 amino acids; 3 triplet codons signify stop No need to memorize this table, but you should be able to APPLY it Fig. 8.3 A gene's nucleotide sequence is co-linear with the amino acid sequence of the encoded polypeptide Charles Yanofsky E. coli genes for a subunit...
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