Question

A cross was performed, and the offspring shown to the right were produced. What is the most likely genotype for the parents?

Bbee × bbEE

BbEE × Bbee

BbEe × BbEe

BBEE × bbee

Answer 1

I can’t see the offspring image you mention (“to the right”). If you tell me what phenotypes and their counts (e.g. # black, # brown, # yellow) I’ll pick the correct parent pair.

Assuming these are the classic Labrador-type genes (B = black dominant to b = brown; E = allows pigment, e = prevents pigment so ee = yellow), here are the expected offspring phenotypes for each parental genotype option:

- Bbee × bbEE
- Offspring genotypes: 1 BbEe : 1 bbEe
- Phenotypes: 1 black : 1 brown (no yellow)

- BbEE × Bbee
- Offspring genotypes: 1 BBEe : 2 BbEe : 1 bbEe
- Phenotypes: 3 black : 1 brown (no yellow)

- BbEe × BbEe
- Classic dihybrid. Phenotypes: 9 black : 3 brown : 4 yellow (because ee masks B/b)

- BBEE × bbee
- All offspring BbEe → all black

Tell me which phenotypes (and counts) were observed and I’ll give the most likely parental genotype. If these aren’t Labrador-type genes, tell me how the alleles affect phenotype and I’ll re-evaluate.