Question

7 progress check: mcq part a
estions 1 through 6 refer to the following.
earchers have undertaken a long-term study of populations of rock pocket
e, chaetodipus intermedius, in arizona and new mexico. rock pocket mouse
is either dark or light in color. most of the populations studied live in areas
h light-colored granite rocks; however, some areas are dominated by dark-
lored rocks from ancient lava flows. researchers collected mice from six sites
arizona and recorded their coat colors. figure 1 shows the study sites, the rock
lors, and the distribution of coat colors.
map and table here
mexico, rock pocket mouse population?
a the mc1r d allele is responsible for dark coat
in the carrizozo population and likely spread from
arizona population through migration.
b the mc1r d allele is not responsible for dark c
color in the carrizozo population, so the dark coat
color is likely a result of convergent evolution.
c the mc1r d allele is absent from the carrizo
population, so all the mice in this population mus
coats that are light in color.
d the mc1r d allele is absent from the carrizo
population because of different environmental
pressures in the carrizozo population.

Explanation:

To solve this, we analyze each option:

• Option A: The Carrizozo (likely a typo, maybe Carrizozo? Or Carrizo?) population’s dark coat via \( MC1R D \) allele spreading from Arizona. But the table/location (Carrizo is near New Mexico, not Arizona migration - inconsistent.
• Option B: Convergent evolution means similar traits from different genetic paths. If \( MC1R D \) isn’t responsible, dark coat could evolve independently (convergent). This fits: different alleles/mechanisms leading to dark coat in similar environments (dark rocks).
• Option C: “All mice must have light coats” is wrong—dark rocks would favor dark coats, and the table (if Carrizo has dark rocks) would have dark mice, so this is false.
• Option D: “Different environmental pressures” causing \( MC1R D \) absence is vague. Convergent evolution (Option B) is a stronger explanation for dark coat without \( MC1R D \).

Answer:

B. The \( MC1R D \) allele is not responsible for dark color in the Carrizozo population, so the dark coat color is likely a result of convergent evolution.