What does the mutation associated with Huntington disease add to the protein?

What does the mutation associated with Huntington disease add to the protein?

• A. Polyglutamine tract
• B. Hydrophilic tract
• C. Phosphorylation site
• D. Disulfide bond

Answer: (A)

The mutation associated with Huntington disease results in the addition of a polyglutamine tract to the protein called huntingtin. This occurs due to an expansion of a CAG repeat in the gene that encodes huntingtin. The normal gene contains a small number of CAG repeats, leading to a protein that functions properly. However, in individuals with Huntington disease, the number of CAG repeats increases significantly, resulting in a long chain of glutamine residues (thus forming a polyglutamine tract) in the huntingtin protein. This abnormal increase in the polyglutamine tract affects the protein's structure and function, ultimately leading to the neurodegenerative effects seen in Huntington disease. The aggregation of this extended polyglutamine region has been linked to cytotoxicity, which contributes to the disease's progression. The other options, such as a hydrophilic tract, phosphorylation site, or disulfide bond, do not accurately characterize the nature of the mutation involved in Huntington disease. These terms refer to different aspects of protein structure and modification, but they do not pertain to the specific alteration that causes the pathology associated with this condition.

The mutation associated with Huntington disease results in the addition of a polyglutamine tract to the protein called huntingtin. This occurs due to an expansion of a CAG repeat in the gene that encodes huntingtin. The normal gene contains a small number of CAG repeats, leading to a protein that functions properly. However, in individuals with Huntington disease, the number of CAG repeats increases significantly, resulting in a long chain of glutamine residues (thus forming a polyglutamine tract) in the huntingtin protein.

This abnormal increase in the polyglutamine tract affects the protein's structure and function, ultimately leading to the neurodegenerative effects seen in Huntington disease. The aggregation of this extended polyglutamine region has been linked to cytotoxicity, which contributes to the disease's progression.

The other options, such as a hydrophilic tract, phosphorylation site, or disulfide bond, do not accurately characterize the nature of the mutation involved in Huntington disease. These terms refer to different aspects of protein structure and modification, but they do not pertain to the specific alteration that causes the pathology associated with this condition.