Question

Huntington disease is caused by a single dominant gene and results in progressive mental and neurological damage. The disease is usually symptomatic when a person is between 30 and 50 years old and the patient usually dies within 15 years of diagnosis. Approximately 1 in 25,000 Caucasians have this disease. Huntington disease has not been associated with any other disease, now or in the past. Why might natural selection not have eliminated such a deleterious gene from the population?

Answer 1

Natural selection may not have eliminated the Huntington disease gene from the population because symptoms typically appear later in life. Additionally, the disease has a low prevalence and may persist through genetic drift.

Step-by-step explanation:

The reason natural selection might not have eliminated the deleterious Huntington disease gene from the population is because the symptoms of the disease typically do not appear until middle age. By the time symptoms present, individuals with the disease may have already passed the gene to their offspring. Additionally, the disease has a low prevalence in the population, affecting only 1 in 25,000 Caucasians. This lower prevalence may have allowed the gene to persist in the population through genetic drift rather than intense selective pressure.