The CGG codon codes for arginine. It is a-amino acid.
By base-pair substitutions, the synonymous changes that can be made with the codon CGG are CGU, CGA, CGC, and AGG. These codons code for arginine.
This is also called synonymous substitution. In this substitution, one base is substituted with another base. One codon for an amino acid is changed to another codon, which codes for the same amino acid.
When a synonymous substitution occurs, the change is considered to be neutral. This is also called silent mutation and this mutation does not cause any alteration in the sequence of amino acid.