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BIOLOGY 12 Single Trait Inheritance and Test Cross Single Trait Inheritance solving problems that involve just one gene with two alleles use a 2x2 Punnett Square have up to 4 possible outcomes Test Cross used to determine the genotype of an individual either homozygous dominant or heterozygous Test Cross example: a black sheep is not preferred because the wool is brittle and difficult to dye black wool is recessive to ensure you will have no black sheep, you must have at least one homozygous dominant parent Test Cross use a test cross to determine the genotype of an individual with a dominant phenotype cross homozygous recessive with the unknown individual Test Cross Test Cross if any of the offspring show the recessive trait, then the parent must be heterozygous Practice for Labrador retrievers, black fur colour is dominant over yellow what would be the genotype of a homozygous black dog? a heterozygous black dog? a yellow female mates with a male with an unknown genotype, if the pups all have black fur, what is the genotype and phenotype of the male? explain. Practice for Dalmatian dogs, the spotted condition is dominant over non-spotted using a punnett square, show the results of a cross between two heterozygous parents a heterozygous spotted female Dalmatian dog mates with an unknown father. from the appearance of the pups, the owner concludes the male was a Dalmatian. the owner notes that the female has 3 spotted and 3 non-spotted pups. what are the genotype and phenotype of the unknown mate?