The sequence below represents the coding DNA strand of the start of a gene, including part of the 5' untranslated region.

(5')...ACCGAAGGAGGTCGCAGCAATGAAACGATTTCGGCACA...(3')

In studying disease variants, a nucleotide mutation of T→C was detected in the third base of the fourth codon. What effect would this mutation have? 

(When considering your answer, assume standard initiation of translation is numbered as codon 1.)