Assuming the gene for coat color expresses complete dominance, the black parental horse must be hybrid -heter0zyg0us-, Bb.
To answer this question, we will assume that the gene involved in coat color expresses complete dominance.
What is complete dominance?
When the dominant allele completely masks the recessive allele expression, we talk about complete dominance.
This is the case of individuals that are heter0zyg0us for a particular gene and express the dominant trait.
The dominant allele is hiding the expression of the recessive allele. Many genes show complete dominance.
Available data:
- The allele for a black coat (B) is the dominant one
- The allele for a brown coat (b) is the recessive one
- cross: black horse with brown horse
- among the F1 there is a brown foal
The brown parental must be bb since this is the recessive trait.
The black parental can be either BB or Bb. The presence of at least one dominant allele B is enough to express the dominant phenotype.
Option 1
Cross: black horse and brown horse
Parentals) BB x bb
Gametes) B B b b
Punnett square) B B
b Bb Bb
b Bb Bb
F1) 100% of the progeny is expected to be Bb expressing black coat.
Option 2
Cross: black horse and brown horse
Parentals) Bb x bb
Gametes) B b b b
Punnett square) B b
b Bb bb
b Bb bb
F1) 50% of the progeny is expected to be heter0zyg0us Bb expressing black coat.
50% of the progeny is expected to be h0m0zyg0us recessive bb expressing brown coat.
The brown parent can provide only recessive alleles b to the progeny, and the black parent can provide either dominant or recessive alleles (B and b respectively).
The black horse must be hybrid -heter0zyg0us-, Bb.
You can learn more about complete dominance at
https://brainly.com/question/1953851
