Huntington disease is an inherited neurodegenerative disease caused by a mutation in the huntingtin gene. When did this mutation arise? García-Planells et al. (2005) found that most Spanish cases of the disease share the same ancestral mutation. Using gene sequence data from patients at genetic loci linked to the mutation, the authors applied a likelihood method similar to that used to date events in the human–ape lineage (Figure 20.2-1). Their calculations produced the following log-likelihood curve for the date of origin of the huntingtin mutation, measured as the number of generations before the present.

(Figure 20.2-1)

a. With the aid of a ruler, use this curve to find the maximum likelihood estimate for the date of origin of the mutation shared by most Spanish cases of Huntington disease.

b. Using this same curve, approximate a 95% confidence interval for the date of origin.

c. What does the interval in part (b) measure? Explain.

Transcribed Image Text:

Gorilla Orangutan Bonobo Chir Chimp Human Orangutan Gorilla Bonobo Chimp Human Orangutan Bonobo Likelihood: e-10133 e-10147 Whitlock & Schluter, The Analysis of Biological Data, 3e © 2020 W. H. Freeman and Company FIGURE 20.2-1 Chimp Gorilla e-10149 Human