Transcript Single Trait Inheritance and Test Cross

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:
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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?