Question

One allele of the APOE gene is associated with early Alzheimer’s disease, while another allele appears to help prevent Alzheimer’s. In a brain cell of an individual with the first type of allele, we find high levels of the protein. In the brain cell of an individual with the second allele, we find no protein.

This indicates the mutation may be found in:

A. an intron in the gene

B. the stop codon

C. the 3' UTR

D. the promoter of the gene

Answer 1

Option D, promoter of gene.  

Promoter is the part of gene where RNA polymerase binds and leads to synthesis of protein. If there is any mutation at this promoter region , than RNA polymerase won't be able to bind at promoter and there will be no protein synthesis.

While other part introns do not appear in mature mRNA and are mon coding part. So it will not affect mRNA and protein synthesis

Stop codon mutation also will not affect protein synthesis as it is present at the last of mRNA

3' UTR is also present just just before poly A tail and not included in protein , so mutation in this part also will not affect the protein synthesis.