Ans.
The codons show genetic codes, made up of triplet of nucleotides in DNA or RNA that code for specific amino acids. The different codes can code for a same a amino acid. When a substitutional mutation occurs in genetic material, it shows substitution of one nucleotide pair for another and leads to formation of a different codon.
The first mutation that leads to CAU to CAC, it will not show any potential damage as both CAU and CAC codons code for histidine amino acid.
The second mutation that leads to UGU to UGC will also not show any damage to protein as both of these codons code for cysteine amino acid.
The third codon, that results UCU to UUU will cause a potential damage to protein as UUU codes for phenyl alanine (an aromatic, non-polar amino acid) and UCU codes for serine (a polar amino acid).
Thus, the correct answer is 'option C).' as in a protein, substitution of serine with phenylalanine will lead to change in structure and function of that protein.
