Question

In one type of dog, black spots (B) are dominant over brown spots (b) and long tails (L) are dominant over short tails (l). Complete a dihybrid cross for parents with the genotypes: BbLL × BBLl and answer the following in complete sentences.

Describe how you would set up a Punnett square for this cross.
List the likelihood of each possible offspring genotype.
List the likelihood of each possible offspring phenotype.

Answer 1

Genotypes of offspring will be BBLL, BbLL, BBLl, and BbLl.

The phenotype of offspring will be all black spots with long tails.

Explanation:

A cross between BbLL and BBLl will form BL, bL, and Bl, BL gametes respectively. All gametes will assort independently and produce offspring of with different genotypes,

The genotype of possible offsprings will be - 25% BBLL (black spot dog with long tail), 25% BbLL (Black spot dog with long tail), 25% BBLl (black spot dog with long tail) and 25% BbLl (black spot dog with long tail)

The phenotype of possible offsprings will be - 100% black spot dog with long tail because there always a copy of dominant alleles are present in the genotype of each offspring.

Answer 2

the punnet square is composed of spots in the x axis and tails in the y axis hence the combinations: | BL | Bl | bL | bl|

The genotypes are
---BL |BBLL| BBLl| BbLL| BbLl
--- bL |BbLL| BbLl| bbLL| bbLl
--- BL |BBLL| BBLl| BbLL| BbLL
--- bL |BbLL| BbLl| bbLL| bbLl