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Double Trait Crosses – Practice Questions
In people, curly hair is dominant over straight hair and the ability to curl the tongue is dominant over not
being able to curl the tongue. A man with curly hair (heterozygous) who has the ability to curl his tongue
(heterozygous) and a woman with curly hair (homozygous) who cannot curl her tongue have children. What
are the possible genotypic and phenotypic ratios of their offspring?
In a dihybrid cross of two pea plants, one is homozygous for two dominant traits and the other is
homozygous for the corresponding recessive traits. What will the genotypic ratio be for the F1 and F2
generations?
Give all of the possible alleles in the eggs of a woman whose genotype is JjKkLl.
In fruit flies, normal wings are dominant over vestigial wings and grey body colour is dominant over ebony
colour. Bugsy, a male fruit fly who is heterozygous for body colour and wing shape, mates with Daisy, a
female fruit fly who is homozygous recessive for body colour and wing shape.
a) Predict the genotypes that will be produced in the F1 generation.
b) What is the probability that a normal winged, ebony coloured fly will be produced?
In the fruit fly, sepia eye colour is recessive to red eye colour, and curved wings are recessive to straight
wings. If a purebred, sepia-eyed, straight-winged fly is mated with a purebred, red-eyed, curved-winged
fly, what phenotypes will appear in the F1 generation? What will the phenotypes be in the F2 generation?
Fruits with seeds are dominant over fruits that are seedless, and blue colour is dominant over purple
colour. A homozygous purple fruit with seeds is crossbred with a homozygous blue, seedless fruit. What
are the genotypes and phenotypes of the F2 generation?
A male and a female guinea pig are both heterozygous for fur colour and texture. Both dark fur and
rough fur are dominant to light fur and smooth fur.
a) Determine the frequency of offspring that are homozygous for both traits.
b) Determine the frequency of offspring that have rough, dark fur.
c) Determine the frequency of offspring that are recessive for both traits.
Double Trait Crosses – Practice Questions
In people, curly hair is dominant over straight hair and the ability to curl the tongue is dominant over not
being able to curl the tongue. A man with curly hair (heterozygous) who has the ability to curl his tongue
(heterozygous) and a woman with curly hair (homozygous) who cannot curl her tongue have children. What
are the possible genotypic and phenotypic ratios of their offspring?
In a dihybrid cross of two pea plants, one is homozygous for two dominant traits and the other is
homozygous for the corresponding recessive traits. What will the genotypic ratio be for the F1 and F2
generations?
Give all of the possible alleles in the eggs of a woman whose genotype is JjKkLl.
In fruit flies, normal wings are dominant over vestigial wings and grey body colour is dominant over ebony
colour. Bugsy, a male fruit fly who is heterozygous for body colour and wing shape, mates with Daisy, a
female fruit fly who is homozygous recessive for body colour and wing shape.
a. Predict the genotypes that will be produced in the F1 generation.
b. What is the probability that a normal winged, ebony coloured fly will be produced?
In the fruit fly, sepia eye colour is recessive to red eye colour, and curved wings are recessive to straight
wings. If a purebred, sepia-eyed, straight-winged fly is mated with a purebred, red-eyed, curved-winged
fly, what phenotypes will appear in the F1 generation? What will the phenotypes be in the F2 generation?
Fruits with seeds are dominant over fruits that are seedless, and blue colour is dominant over purple
colour. A homozygous purple fruit with seeds is crossbred with a homozygous blue, seedless fruit. What
are the genotypes and phenotypes of the F2 generation?
A male and a female guinea pig are both heterozygous for fur colour and texture. Both dark fur and
rough fur are dominant to light fur and smooth fur.
a. Determine the frequency of offspring that are homozygous for both traits.
b. Determine the frequency of offspring that have rough, dark fur.
c. Determine the frequency of offspring that are recessive for both traits.