Question

SC.912.L.16.1 (high)

5. Coat color in Labrador retrievers is determined by genes at two loci, B, and E, where B
and E are dominant, and b and e are recessive. The genes follow the Mendelian law of
independent assortment. Black dogs must have at least one dominant allele for both B
and E. Chocolate colored dogs must have at least one dominant B, and be homozygous recessive for e. True yellow dogs must be homozygous recessive at both
loci. If two dogs with genotypes BbEe and BbEe are bred, what is the probability that
they will have a puppy that has the genotype of a true yellow dog?
A. 1 in 16
B. 3 in 4
C. 3 in 16
D. 9 in 16

Answer 1

Answer: 3 in 16

Explanation: BbEe provides the most possible combinations for offspring in labs. This is because each dog can possibly give two of any of the genes. Yellow labs can only have two little e genes (ee), if they have a single E gene, they will either be brown or black. But within the ee genes, they can have two other combinations of their other genes. All combinations for a yellow lab are:

Bbee

BBee

bbee

But those are only the yellow combinations, there are 13 other combinations. Making it a 3/16 chance.