Random mutations may occur because a change in the order of nitrogen bases in a codon. One type of mutation involves a substitution of one of the nitrogen bases in a codon. What amino acid is called for by GGA codon?

Alanine

Explanation:

Using the codon chart (see the attached image), that is, a chart of triplet codes and the corresponding amino acids that they represent, the amino acid called for by GCA codon is alanine.

There are 64 possible codons in nature from 4 nitrogen bases - adenine (A), guanine (G), cytosine (C), and uracil (U). The codes are degenerates because they represent only 20 naturally occurring amino acids. Hence, more than one codons codes for each amino acid. Apart from GCA, other codons that translate as alanine include GCU, GCC, and GCG.