Question

An animal's black coat color (B) is dominant to brown (b). If a black individual is mated with a brown one and the offspring are 3 black and 2 brown puppies. What can you conclude about the genotype of the black parent?

1) The genotype must be BB.
2) The genotype must be bb.
3) The genotype must be Bb.
4) The genotype could be either BB or Bb.
5) The genotype cannot be determined from this data.

Answer 1

The genotype of the black parent with a brown mate that produced both black and brown puppies 3) must be Bb (heterozygous), as this allows for the offspring to have both black and brown coat colours.

Step-by-step explanation:

The question addresses Mendelian genetics, specifically the inheritance of coat colour in animals, where black coat colour (B) is dominant to brown (b). Given that mating a black individual with a brown one resulted in 3 black and 2 brown offspring, it is possible to deduce the genotype of the black parent. Since there are brown puppies among the offspring, the black parent must have contributed a recessive b allele to produce them. Thus, the black parent cannot have a genotype of BB (which would result in only black offspring). The genotype of the black parent cannot be bb, as this would result in brown coat colour. Therefore, the only possible genotype for the black parent that explains the observed coat colours is Bb.

Answer 2

The correct conclusion about the genotype of the black parent is (4) The genotype could be either BB or Bb. Thus the correct optuion is 4.

Step-by-step explanation:

The observed ratio of 3 black to 2 brown puppies suggests a genetic combination involving a heterozygous black parent (Bb). This is because in Mendelian genetics, when a dominant trait (B for black) is crossed with a recessive trait (b for brown), a 1:1 ratio of phenotypes is expected among the offspring. However, since the observed ratio is 3:2 in favor of black, it indicates the presence of at least one dominant allele in the black parent's genotype.

Let's denote the genotype of the black parent as B_ (with the blank representing the unknown allele). If it were homozygous dominant (BB), all offspring would be black. If it were homozygous recessive (bb), all offspring would be brown. The observed 3 black and 2 brown puppies align with the expected outcome of a heterozygous parent (Bb), resulting in a 3:2 ratio. Therefore, the conclusion is that the black parent's genotype could be either BB or Bb.

This scenario showcases the principles of Mendelian inheritance and the importance of observing phenotypic ratios in deducing potential genotypes. The ambiguity arises because the observed outcome could result from multiple genetic combinations, highlighting the complexity of genetic inheritance.