Question

The human immunodeficiency virus (HIV) causes AIDS, a disease of the immune system that culminates in death. To mount a successful invasion, the HIV virus must bind to a protein known as CCR5 that resides on the surface of immune cells. Individuals that are homozygous for a deletion of the CCR5 gene are completely protected from HIV infection. The CCR5 gene is transcriptionally silenced by Xp1, a negative regulator of CCR5 that is expressed everywhere but the immune system. Given this information, would you expect the following mutations to be dominant or recessive to their normal (functional) alleles in terms of HIV infection? Briefly justify each of your answers.

(a). A mutation in the CCR5 gene that creates a stop codon in the middle of the coding sequence.

(b). A mutation in the promoter region of the CCR5 gene that prevents a positively acting transcription factor from binding.

(c). A mutation in the promoter region of the CCR5 gene that allows a negatively acting transcription factor to bind to the promoter region.

(d). A mutation in the promoter region of the Xp1 gene that switches Xp1 on in the immune system.

please give a small explanation of why it is dominant or recessive.

Answer 1

a. Recessive, as the genes without the mutation are still being produced normally, and the infection will proceed with those proteins.

b. Dominant, as binding is prevented in all copies of the gene

c. Dominant, as all gene copies bind the negative transcription factor.

d. Dominant, as the immune system will active against all copies of the protein in the body.