Awhite dog is crossed with a heterozygous black dog. what are the pearents genotype ? and what percentage of the offspring will be black ?

The black heterozygous dog has the genotype "Aa" and the white dog has the genotype "aa". A cross between these two dogs (Aa x aa) would generate an offspring of 50% Aa (black coat) and 50% aa (white coat).

Explanation:

Heterozygous organisms have the characteristic of the dominant allele, so we can say that the black dog shown in the question above has the "Aa" alleles in its genome. As black fur is a dominant characteristic, we can consider the white dog as a homozygous recessive dog, therefore it has the "aa" genotype. If we crossed these two dogs we would have an "Aa x aa" type crossing that would result in an offspring with the genotypes "Aa", "aa", "Aa", "aa". In this case, 50% of the offspring have the "Aa" genotype and 50% of the offspring have the "aa" genotype.

a chair, a bed, and a toothbrush

explanation: