A client learns that Huntington disease has occurred in some family members. Which type of genetic anomaly should the nurse explain as causing this disorder?

Question

1. Somatic mutation
2. Germline mutation
3. Single gene mutation
4. Trinucleotide repeat expansion

Answer 1

4
Explanation:
1. Somatic mutations are DNA alterations that occur in an individual at any time throughout a lifetime after fertilization. They result from errors during cell division (mitosis) or from environmental influences such as radiation, toxins, or viral infections and are not passed from one generation to another.
2. Germline mutations exist in the reproductive cells, causing the DNA in every cell of any offspring to have the mutation, which can then be transmitted to following generations.
3. Single gene mutations are known to cause diseases such as cystic fibrosis.
4. Trinucleotide repeat expansion occurs at sites within a gene where the DNA sequence consists of adjacent three-nucleotide repeats. These repeat sequences tend to expand during meiosis, a feature known as anticipation, resulting in a larger number of repeats in subsequent generations.
A larger number of repeats may be associated with disease; typically, the larger the number of repeats, the more severe the condition. Huntington disease is caused by this type of genetic anomaly.