What are the genotypes of offspring that could occur if a heterozygous cat is mated with a white cat and in cats, yellow fur is dominant over white fur?
The question states that yellow fur is dominant over white fur. Given that the alleles for these two traits are a capital Y and a lowercase y, the genotype for the heterozygous cat would be 'Yy' and the genotype for the white cat would be 'yy' since white fur is recessive.
Therefore, if you cross a 'Yy' with a 'yy' the only two genotypes you would get from the punnett square would be 'Yy' and 'yy'.
The only way you would be able to attain a genotype of 'YY' would be if both cats were heterozygous.