Question

There is a population of alien dogs, species Dogus Cute-ee-us, that live on the planet Woof. Their genomes and biology are amazingly identical to the genomes and biology of earth dogs. Consider a di-hybrid cross, where the first locus has alleles A and a, and second locus has alleles B and b. Each additional copy of either an A or B allele in the two-locus genotype increases the friendliness of the dog. Friendliness is measured by the Wilcoxon-Canus Amicus Diagnostic Scale (WCADS). There are five categories:

0 = Unfriendly/Loner (although not aggressive);

1 = Somewhat friendly/shy;

2 = Friendly;

3 = Very friendly;

4 = Maximally friendly.

For example, an alien dog with a two-locus genotype of Aabb would have a Somewhat friendly/shy behavior, since there is one copy of A and zero copies of B, adding to a score of 1 for the WCADS. Similarly, an alien dog with a two-locus genotype of AaBB has a Very friendly behavior (one copy of A + two copies of B = three copies total of A or B).

In the following mating: AaBb x AaBb, you compute an expected ratio of Maximally friendly:Very friendly:Friendly:Somewhat friendly:Unfriendly alien dogs in the offspring. Assuming the parents produce a very large litter, how many degrees of freedom are there for the Chi-square statistic that tests the validity of your computed expected ratios?

A. Question cannot be answered with the information given

B. 4

C. 5

D. 2

E. 3

Answer 1