A mutation in a gene in the fruit fly Drosophila was found to affect eye color. The protein affected was found to be completely normal in its molecular weight and amino acid sequence, although much less of the protein is made in mutant flies. A reasonable explanation for the change in levels of protein is that the mutationA. causes the stop codon to be replaced by a sense codon.B. is a frame shift mutation near the start of the coding region.C. affects the splicing of the mRNA.D. occurs in the promoter of the gene, within several hundred base pairs of the start of transcription.E. is a change of a codon for serine into another codon for serine.

The correct option is D. A reasonable explanation for the change in levels of protein is that the mutation occurs in the promoter of the gene, within several hundred base pairs of the start of transcription.

Explanation:

In genetics, a promoter can be described as a region where the RNA polymerase binds initially and starts transcription. The promoter is usually present near to the gene that has to be transcribed. The rate of transcription is controlled by the promoter region too. Hence, the correct option is D. The promoter region for the eye colour was changed due to mutation.

Other options are false because a change in a codon or base pair would have changed proteins being formed and would not have slowed the process.