Which amino acid is specified by genetic codes ACU, ACC, ACA, ACG showing degeneracy?
Genetic code shows degeneracy which means that multiple codons specify particular amino acid. Amino acid leucine is encoded by 6 codons; UUA, UUG, CUU, CUC, CUA and CUG, thus it shows degeneracy but is not encoded by codons given in the question which makes option A wrong. Methionine is the exception to code degeneracy as it is encoded by single codon “AUG” which makes option B wrong. Glycine is encoded by GGU, GGC, GGA and GGG; thus shows code degeneracy but is not specified by codons mentioned in question which makes option C incorrect. Threonine is encoded by multiple codons ACU, ACC, ACA and ACG; option D is the correct answer.