What did researchers discover about the mutant form of the TYR gene?
1) It has a deletion of a single guanine nucleotide in the beginning of the coding sequence.
2) It has a duplication of a single guanine nucleotide in the beginning of the coding sequence.
3) It has a substitution of a single guanine nucleotide in the beginning of the coding sequence.
4) It has an insertion of a single guanine nucleotide in the beginning of the coding sequence.