HW 2
Name: __
APPLYING HARDY-WEINBERG TO ROCK POCKET MOUSE FIELD DATA
Dr. Nachman and his colleagues collected rock pocket mice across 35
kilometers of the Arizona Sonoran Desert, which included both dark, rocky
lava outcrops and light, rocky, granite areas. They recorded substrate color
and coat-color frequencies for each location. Each site was separated from
any of the others by at least eight kilometers. The researchers trapped a
total of 225 mice. Their data are summarized below.
Collecting Site
Substrate Color
Number of Mice
Phenotype
Light
Dark
1
Light
6
6
0
2
Light
85
80
5
3
Dark
7
0
7
4
Dark
5
0
5
5
Dark
45
3
42
6
Light
77
34
43
Source of data: Hoekstra, Hopi E., Kristen E. Drumm, and Michael W.
Nachman. Ecological Genetics of Adaptive Color Polymorphism in Pocket
Mice: Geographic Variation in Selected and Neutral Genes. Evolution 58, no.
6 (2004): 13291344.
QUESTIONS
1. Calculate the overall frequencies of light-colored mice and dark-colored
mice caught on light-colored substrates. Frequency = number of mice of one
color/total number of mice
Frequency of light-colored mice ___.54___ Frequency of dark-colored
mice __.453__
2. Calculate the overall frequencies of light-colored mice and dark-colored
mice caught on dark-colored substrates. Frequency = number of mice of one
color/total number of mice
Frequency of light-colored mice ___.05_____ Frequency of dark-colored
mice __.94___
3. Using the Hardy-Weinberg equation and data from the table above,
determine the number of mice with the DD and Dd genotypes on the light,
rocky, granite substrate.
Frequency of mice with the dd genotype on light-colored substrate
___.71_____
Frequency of mice with the DD genotype on light-colored substrate
___.28_____
Frequency of mice with the Dd genotype on light-colored substrate
____.28____
4. Using the Hardy-Weinberg equation and data from the table above,
determine the number of mice with the DD and Dd genotypes on the dark,
rocky lava substrate.
Frequency of mice with the dd genotype on dark-colored substrate
__.05______
Frequency of mice with the DD genotype on dark-colored substrate
___.94_____
Frequency of mice with the Dd genotype on dark-colored substrate
___.94_____
5. Which fur color seems to have the greatest overall selective advantage?
Use data collected from both dark-colored and light-colored substrates to
support your answer.
Light colored fur, the overall frequency of light colored mice is greater than
that of dark colored mice.
6. According to the film, what environmental change gave a selective
advantage for one coat color over another?
The color of the landscape changed so that some members of the population
were more visible to predators than other members were.
7. In a separate study, 76 rock pocket mice were collected from four
different, widely separated areas of dark lava rock. One collecting site was in
Arizona. The other three were in New Mexico. Dr. Nachman and colleagues
observed no significant differences in the color of the rocks in the four
locations sampled. However, the dark-colored mice from the three New
Mexico locations were slightly darker than the dark-colored mice from the
Arizona population. The entire Mc1r gene was sequenced in all 76 of the
mice collected.
The mutations responsible for the dark fur color in the Arizona mice were
absent from the three different populations of New Mexico mice. No Mc1r
mutations were associated with dark fur color in the New Mexico populations.
These findings suggest that adaptive dark coloration has occurred at least
twice in the rock pocket mouse and that these similar phenotypic changes
have different genetic bases. How does this study support the concept that
natural selection is not random?
When different genetic mutations produce the same phenotypes in different
areas, these similar adaptations are favored under similar conditions.
8. To determine if the rock pocket mouse population is evolving, explain why
it is necessary to collect fur color frequency data over a period of many
years.
So see if the frequency of fur colors changes with changes in the
environments color.
