Bovine insulin is composed of 30 amino acids. What is the minimum number of DNA triplets in the insulin gene, based on the amino acid length? What is the minimum number of DNA bases in the coding region? Explain how and why the actual number of triplets in the gene may differ.
What will be an ideal response?
Ignoring stop and start codons, RNA splicing, and post-translational modification, a peptide of 30 amino acids is specified by 30 triplets. As a triplet is 3 bases in length, this means a minimum of 90 DNA bases (30 triplets × 3 bases per triplet) is present in the insulin gene. The actual number of triplets and bases is higher, because the gene starts and ends with start and stop sequences, some of the mRNA codons are excised prior to translation and peptide sequence, and furthermore post-translational modification of the peptide may remove additional amino
acids. Thus the number of amino acids in the peptide is related to gene length but doesn't allow precise calculation of gene length.
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