a) The resulting changes in mRNA codon would be;
CAU TO CAA; This because in the mRNA the base Thyamine is replaced by cytocine, therefore A would pair with Cytosine.
B) The effect on the corresponding amino acid would be a change from His to Gln. This mutation would result to a change form Histidine to Glutamine; this is because the codon CAU codes for Histidine while CAA codes for Glutamine.