Genetic Test Review
Topics: 4.1-4.3; 10.1-10.3
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Meiosis
Nondisjunction disorders
Mendelian Genetics:
o Monohybrid crosses, incomplete dominance, co-dominance, multiple allelism,
dihybrid crosses, test crosses, sex linkage, polygenic inheritance, autosomal
linkage
Pedigrees
Mendelian Genetics Problems
1. A mouse with grey fur was mated with a mouse with white fur. Both mice were
homozygous. All the F1 offspring had grey fur.
a) Which trait is dominant? Which trait is recessive?
b) What are the genotypes of the parents?
c) What are the genotypes of the F1 mice? Prove it with a punnet square.
d) Two F1 mice mate. What are the genotypic and phenotypic ratios of the F2
generation.
2. In unicorns the allele for long horns is incompletely dominant over no horns.
Heterozygotes have short horns.
a) If a long horned unicorn mated with a hornless unicorn, give the expected
genotypic and phenotypic ratios of the F1 generation.
b) If a hornless unicorn mated with a short horned unicorn, give the expected
genotypic and phenotypic ratios of the F1 generation.
3.
In a certain breed of cattle, the gene for fur coat colour is co-dominant. What is
the possibility that a red cow and a roan bull will have:
a) A white offspring?
b) A red offspring?
c) A roan offspring?
4. A man with type AB blood marries a woman with type A blood. What are the
expected genotypic and phenotypic ratios of their children if:
a) The woman was is homozygous for the A allele
b) If the woman’s father has type O blood.
5. A type A blood woman whose father has type O blood, marries a type B blood man
who’s mother has type O blood. What are the expected genotypic and phenotypic
ratios of their children?
6. In mice, brown fur dominates over grey fur, and long tails dominate over short tails.
a) What is the phenotypic ratio of a cross between two mice that are
heterozygous for both traits.
b) In mice, brown fur dominates over grey fur, and long tails dominate over short
tails. A brown, short tailed mouse mates with a grey long tailed mouse. All 50 of
the F1 generation mice are brown with long tails. What are the genotypes of the
parents and the F1 mice?
7. In a particular species of corn, purple kernels dominate over yellow kernels. When
purple kernel was test crossed, the F1 generation was contained 40 purple kernels
and 42 yellow kernels. What was the genotype of the original purple kernel parent?
8. In the same species of corn (mentioned in #7), smooth kernels dominate over
wrinkled kernels. When a purple and smooth kernel was test crossed, the following
was produced in the F1 generation: purple & smooth = 20; purple & wrinkled = 23
yellow & smooth = 19; yellow & wrinkled = 25. What was the geneotype of the parent
kernel?
9. Ben is a hemophiliac but his brother Nathan is not. Assuming, their father Tyler is
normal,
a) what is the probability that their sister Marianne is a hemophiliac?
b) what is the probability that Marianne is a carrier for hemophilia?
c) What is the probability that their other brother Luke is a hemophilac?
10. Sherry is colour blind but her husband Ryan has normal vision. What is probability
of them having:
a) A colour blind son?
b) A colour blind daughter?
c) A normal sighted child?
11. In a particular species of cats there are 4 eye colour phenotypes: blue, green,
amber, and brown. Eye colour is controlled by 3 genes – genes A, B, and C. If a cat
has only recessive alleles (aabbcc), the cat will have blue eyes. The presence of at
least 1 dominant allele for 1 gene, will result in green eyes. (ie: Aabbcc , and aaBBcc,
and aabbCc will all have green eyes.) The presence of at least 1 dominant allele for
2 genes will result in amber eyes (ie. AAbbCc and aaBBCC will both have amber
eyes). The presence of at least 1 dominant allele for all 3 genes will result in brown
eyes (AABBCC and AaBbCc will all have brown eyes). What is the expected
phenotypic ratio when a AaBBCc cat mates with a aabbCC cat?
12. In a particular species of tomato, the trait for red tomatoes (R)dominates over
green tomatoes(r). Another gene controls whether a colour pigment will be
deposited at all. The trait for colour (A) dominates over the trait for no colour (a).
(Tomatoes with no colour appear yellow.) If a AaRr tomato plant is crossed with a
Aarr tomato plant, give the expected phenotypic ratio of the F1 generation.
Use the following pedigree to answer questions #13 -
13. In the pedigree, the black shapes represent individuals with hemophilia.
a) List all the possible geneotypes of everyone in this family tree (for some members,
there may be more than one answer).
b) What is the genotype of carrier of hemophila?
c) List all the carriers of hemophilia in this pedigree.
d) If Rick and Celina have a son, what is the probability that he will be hemophilac.
e) Explain how you can tell that hemophilia is not a dominant trait just by looking at
the pedigree.
14. Jeanne has type A blood, Alma has type B, and Lindsay has type O. Angela has type
O blood and Alan has type AB blood. Jonathan and Connie have type B blood and
Alberto has type O blood. What are the genotypes of Alma and Rick?
15. If Alan and Rick have normal vision and Angela is a carrier the colour blind allele,
what is the probability that
a) Craig is colour blind?
b) Celina is colour blind?
c) Celina is a carrier?
16. In mice black hair colour I dominant to brown hair colour and a straight tail is
dominant to curly tail. If a black mouse with a curly tail, whose mother had been a
brown mouse with a curly tail, is crossed with a homozygous brown mouse with a
straight tail, what are the possible phenotypes and genotypes of the offspring.
17. In guinea pigs, rough coat (R) is dominant to smooth coat (r) black coat (B) is
dominant to white coat (b). Predict the genotype and phenotype ratios of a cross
between a heterozygous rough, black coat male guinea pig and a black coat, smooh
coat female which was fathered by a white, smooth coat mouse.