You Are Studying a Coat Color Gene (B, Brown) in Mexican

Essay

You are studying a coat color gene (B, brown) in Mexican bats. You have isolated a recessive allele (b) that causes yellow coat color, but you suspect that the phenotype may be sensitive to environmental conditions. To test your hypothesis, you examine the segregation ratio of phenotypes in F₁ progeny from a cross between two heterozygotes. You do this once at normal laboratory temperatures (28°C) and once at temperatures closer to their native habitat (34°C) and record the following data: $$\begin{array} { l l l } & \text { Brown } & \text { Yellow } \\28 ^ { \circ } \mathrm { C } & 153 & 47 \\34 ^ { \circ } \mathrm { C } & 170 & 30\end{array}$$ a. What ratio do you expect in each experiment if temperature does not affect the phenotype?
b. What test can you use to determine if the ratio you observed is significantly different from the expected ratio?
c. Using that statistical test, is either observed ratio more different from the expected ratio than one would expect from chance alone? If so, suggest a biological explanation.