Question

“Florida mice” essay question

Describe Hopi Hoekstra’s evidence for how coloration for Atlantic coast beach mice of Florida evolved independently from coloration for Gulf coast beach mice of Florida. Be specific in terms of the different genetic mechanisms associated with the formation of a similar phenotypic trait across the two beach mice populations. How did Hopi Hoekstra test the fitness (differential survival) associated with the presence or absence of the coloration trait in the beach mice? How do we know that the pale coloration trait of beach mice was derived from the ancestral coloration of mainland mice, and not vice versa? How could you test to see whether the change in coloration trait was heritable and not just a consequence of phenotypic plasticity?

Answer 1

a)

Hopi Hoekstra found that a single amino acid substitution in the first intracellular region of the Mc1R protein (arg⁶⁵cys) is associated with the pale coloration of gulf coast beach mice of florida. by contrast, they found that Atlantic coast beach mice of Florida do not harbour 65 cys mutation, which suggests that coloration for Atlantic coast beach mice of Florida evolved independently from coloration for Gulf coast beach mice of Florida and different genes might be responsible for the convergent phenotypes.

the reason for different genetic mechanism associated with the formation of a similar phenotypic trait across the two beach mice populations is,

genetic variations are random in different populations - which arise due to random changes in the DNA and subsequently in protein sequence. but due to similar selection pressure (dark coloured individuals will be spotted frequently in beach area ) in the two different populations, those individual got selected who had mutations that made them pale coloured hence prevented them from predators.

b)

Hopi Hoekstra tested the fitness of coloration trait in beach mice by making plastic models of mice with beach and mainland coloration and placing them in the feild. Predatory attacks were scored by the presence of bite marks, bill marks, dragging of models, or other injuries.The proportion of attacked model mice that matched or mismatched their habitat were calculated (relative to the total number of mice attacked).

c) How do we know that the pale coloration trait of beach mice was derived from the ancestral coloration of mainland mice, and not vice versa?

Ans. Mainland mice population was found to show greater genetic variability in the genes coding for pale coloration(ex-Mc1R) as compared to the beach population, which shows that beach mice population was founded by a few individuals from the mainland mice populations.

d) How could you test to see whether the change in coloration trait was heritable and not just a consequence of phenotypic plasticity?

Ans. take the pale colored mice out of its habitat (i..e beach) to the mainland or laboratory and allow them to breed there. if the progeny continues to be pale colored in every generation then it confirms that change in coloration trait is heritable and not just a consequence of phenotypic plasticity.