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MONOHYBRID PRACTICE PROBLEMS
1) In humans, curly hair is dominant over straight hair. A woman heterozygous for hair curl marries a man with straight
hair and they have four children.
a) Show the parental cross and the possible gametes produced.
b) Use a Punnett square to find the possible genotypes for the F2 generation.
c) What are the phenotypic and genotypic ratios of the F1?
d) What is the probability that the first child will have curly hair? What is the probability that the third child will have curly
hair?
2a) Show the cross between a woman who is homozygous normal for vision and a man who is homozygous for
glaucoma. Glaucoma is dominant to normal vision.
b) If there are four grandchildren (F2 generation) all having parents (F1) with the same genotype, how many of these
children will have glaucoma?
c) What is the probability of each grandchild having glaucoma? What is the probability of each child having normal
vision?
3) Give the phenotypic and genotypic ratios of the possible offspring produced, when a heterozygous brown-eyed man
marries a heterozygous brown-eyed woman. Brown eyes are dominant over blue eyes which are recessive.
4) Two brown-eyed parents have two children with blue eyes. Give the genotypes of each member of the family.
5) Albinism (lack of pigment) in humans is caused by a recessive gene. If normal parents have an albino child, what is the
probability that their next child will be normal for pigment?
6a) Free ear lobes are dominant to attached ear lobes in humans. If a homozygous, recessive male marries a
homozygous dominant female, what will be the phenotypic and genotypic ratios of their offspring?
b) If one of these female children were to marry a man with her genotype, what would be the phenotypic ratio of their
children?
7) A homozygous, dominant individual for long eyelashes is crossed with a heterozygous individual. What is the
probability that they will produce offspring without long eyelashes? Long lashes is dominant; short lashes is recessive.
8) The ability to taste the drug phenyl-thio carbamide (P.T.C.) is due to a dominant gene. A non-taster man marries a
taster woman whose father was a non-taster.
a) What will be the expected genotypes of their four children?
b) What would be the expected phenotypes for ten children?
c) What is the probability that their first child has the heterozygous genotype?
GAMATE PRACTICE PROBLEMS
List all the gametes that are possible with each of the following genotypes.
a. Aabb ___________________________ d. AABb ____________________________
b. AaBB ___________________________ e. AAbb ____________________________
c. AaBb ___________________________ f. aabb ____________________________
PROBABILITY PRACTICE PROBLEMS
What is the probability of each of the following sets of parents producing the given genotypes in their offspring?
Parents Genotype
Offspring Genotype
Probability
Aa x Aa
Aa
Aa x aa
Aa
AaBb x AaBB
AABB
AaBb x AABb
aabb
AaBb x AaBb
AaBb
DIHYBRID AND MULTICHARACTER PRACTICE PROBLEMS
MendAliens are from the plant LaneTechius. In MendAliens, black eyes are dominant to orange eyes. They
usually have green skin, which is dominant but they can have white skin. Some MendAliens are 4 feet tall, which
is dominant to being 2 feet tall. Four eyes is dominant to having 2 eyes and straight horns are dominant to curly
horns.
1. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is
MendAlien with orange eyes and white skin. If Sam and Carole were to mate, what are the phenotype
probabilities of their offspring?
2. Matthew the MendAlien is heterozygous for horn shape and height. He marries and mates with Mandy, who is
also heterozygous horn shape and height.
a. What is the possibility that their offspring will be tall with curly horns?
b. What is the possibility that their offspring will be tall with straight horns?
c. What is the possibility that their offspring will be short with curly horns?
d. What is the possibility that their offspring will be short with straight horns?
e. What is the possibility that their offspring will have the same genotype as the parents?
f. What is the possibility that their offspring will have a recessive genotype for horn shape but be
heterozygous for height?
3. In a cross AaBbCcDd  AaBbCcDd,
a. what is the probability of producing the genotype that is identical to the parents?
b. what is the probability of producing an offspring with a homozygous recessive for all genes?
c. Assuming complete dominance, what is the probability of producing the phenotype that is identical to the
parents?