A test cross of AaBb x aabb produced 1000 offspring. Expected ratio under independent assortment is 1:1:1:1 (250 each). Observed: 420, 80, 75, 425.
The skewed distribution is best explained by:
- A
Sampling error in a large population.
- Bcheck_circle
Genetic linkage; AB and ab are parental gametes, Ab and aB are recombinants.
- C
Independent assortment producing equal frequencies.
- D
Codominance of the alleles.
Explanation
Excess parental-type offspring (AB and ab) plus a small recombinant class (Ab, aB) indicates the loci are linked on the same chromosome. Map distance ~ (80+75)/1000 x 100 = 15.5 cM.