Stop codons are all except -

Ans. is 'd' i.e., UGG* Out of 64 codons, 3 are stop codons. The three stop codons are UGA, UAG, UAA.# Exception is mitochondrial DNA - in mitochondria, UGA is not a stop codon. It codes for Tryptophan. Instead AGA and AGG act as stop codons in mitochondrial DNA.* 61 codons code for 21 aminoacids. Hence more than one codon code for a single aminoacid. This is called as degeneracy of Codon.# Exceptions are Methionine and Tryptophan. Both Methionine and Tryptophan are coded by only one codon each# Methionine is coded by AUG and Tryptophan is coded by UGG* Hence UGG is not a stop codon. It codes for Tryptophan