Download Genetics Review Problems

Smorgasbord Review #2
NAME:__________________________
1. Flower color in snapdragons can be red, white, or pink. Pink snapdragons occur when the genotype is
heterozygous. Two pink snapdragons are crossed. What are the phenotypes of their offspring and in what
proportion?
2. Coat color in cattle can be red, white, or roan (both red and white). If 2 roan cattle are crossed, what are the
phenotypes of their offspring and in what proportion?
3. A rabbit breeder wants to get as many white-haired, red-eyed rabbits as possible. However, these are both
recessive traits and the 2 parent rabbits have gray hair and black eyes. How many white-haired, red-eyed
rabbits will result if both parents are heterozygous for both traits?
4. Color-blindness is a sex-linked recessive disorder. If Don is not colorblind and his wife, Betty, is not
colorblind, would it be possible for them to have children who are colorblind? Show the cross to prove it.
5. Two people, one heterozygous for type A blood and one who is homozygous for type B blood have children.
What is the phenotypic ratio? ____________________
6. The gene for colorblindness is carried on the X chromosome and is recessive. A man, whose father was
colorblind, has a colorblind daughter.
a.) Is this man colorblind? _________ How do you know?
b.) Where did he get his gene for colorblindness?______________________________
c.) Must the fathers of all colorblind girls be colorblind? __________Why?
7. Hornless (H) in cattle is dominant over horned (h). A homozygous hornless bull is mated with a homozygous
horned cow. What will be the genotype and phenotype of the first generation?
8. In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the
allele for white is W. The heterozygous phenotype is known as erminette (black and white spotted). If two
erminette chickens were crossed, what is the probability that:
Parents: ____ X ____
a. They would have a black chick? ____%
b. They would have a white chick? ____%
9. In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The
recessive trait causes mice to run in circles only. Mice with this trait are called waltzing mice (r). Hair color is
also inherited in mice. Black hair (B) is dominant over brown hair (b). Cross a heterozygous running,
heterozygous black mouse with a homozygous running, heterozygous black mouse. Write the genotypic and
phenotypic ratios.
Practice Pedigrees
11. Marfan syndrome is an autosomal dominant condition that affects the connective tissue, resulting in
unusually long bones and spinal curvature, as well as vision, cardiac, and respiratory problems. The syndrome
tends to become increasingly severe over time. The following pedigree shows inheritance of Marfan
syndrome in a multigenerational family.
a) Can you determine individual II-4’s genotype?_________ Explain.
b) What individual has a genotype that you cannot determine?_____________
c) Individual II-1 and II-2 are considering having another child. What is the probability that this child will have
Marfan syndrome? __________Explain using a Punnett square.
12. Jason is a 12 year old boy with no history of familial hypercholesterolemia in his family and has dreams of
marrying his 10 year old neighbor Michelle when they become older. Michelle’s mother and father are both not
affected by familial hypercholesterolemia, but she has been tested and she does have hypercholesterolemia.
Jason has just learned about genetics in school and wants to predict the health of their future children. He has
always wanted 2 children. Draw a pedigree that includes every person mentioned in the story. Include a Punnett
square of the Jason and Michelle.
Draw your pedigree of the 6 people below(You do not need to include Jason’s and Michelle’s offspring)
a.) Write in the probable genotype below each circle and square on the pedigree above.
b.) What is the probability that a child will become affected by familial hypercholesterolemia?_________