The four nucleotides found in human DNA (G, A, T, and C) combine in groups of th

Question

The four nucleotides found in human DNA (G, A, T, and C) combine in groups of three to create 64 different amino acids, but only 20 amino acids and two start/stop codons are used to construct proteins. Why is this so? (Please Elaborate)

64 amino acids are produced, but 42 of them are unstable and degraded immediately

64 amino acids are produced, but the body only integrates 42 of them into proteins

Different nucleotide combinations code for the same amino acid

Many amino acids are not complete until they bind to a second amino acid

64 amino acids are produced, but 42 of them are unstable and degraded immediately

64 amino acids are produced, but the body only integrates 42 of them into proteins

Different nucleotide combinations code for the same amino acid

Many amino acids are not complete until they bind to a second amino acid

Explanation / Answer

Different nucleotide combinations code for the same amino acid

Some of the amino acids can be coded by more than one but specific triplet nucleotide combinations. This unique feature of triplet codons is referred to as degeneracy. For example, an amino acid Arginine can be represented by any one of the triplet codon among the following 6 nucleotide combinations: CGU, CGC, CGA, CGG, AGA, AGG.

All other amino acids except methionine and tryptophan (represented by only single codon sequence) exhibit degeneracy of genetic code. Start codon (AUG) is represented by a single nucleotide combination whereas stop codon (UAA, UGA, UAG) can be encoded by any of the 3 triplet codons.

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