Download Practice Problems Sex Linked, Multiple Alleles, Genetic Disorders

A Plethora of Punnett Squares!
• Sex-linked!
• Multiple Alleles (Blood typing)!
• Genetic Disorders!
*remember to show your Punnett squares*
Sex-linked #1
Humans are able to detect color because of a dominant
gene carried on the X chromosome. The recessive allele
produces red-green color blindness. A man with normal
color vision marries a female who carries a recessive
gene, although her vision is normal.
a. What are the genotypes of the P generation?
b. What are the F1 male genotypes and phenotypes?
c. What are the F1 female genotypes and phenotypes?
Sex-linked #2
A hybrid (heterozygous) woman from the previous
cross marries a colorblind male.
a. What are the genotypes of the woman and man?
b. What are the F2 male genotypes and phenotypes?
c. What are the F2 female genotypes and phenotypes?
Sex-linked #3
One of the sons from the previous mating is involved
in a paternity suit. The child in question is a
colorblind female. The judge rules that the child
could not possibly belong to this man.
a. Which son of the parents in problem 2 was involved in this
case? Give his genotype and phenotype.
b. Explain your answer.
Sex-linked #4
If a woman is a carrier for a mutation causing a sex-linked
disorder, what is the chance that one of her sons will
have the disorder? Explain your answer.
Multiple Alleles: Blood Typing #1
In humans, the blood types A, B, AB and O are
determined by the three alleles A, B, O. A man
who has AB blood marries a woman with O blood.
a. What are the genotypes of the P generation?
b. What are the F1 genotypes and phenotypes?
Multiple Alleles: Blood Typing #2
A man who is heterozygous Type-A marries a
woman who is heterozygous Type-B.
a. What are the genotypes of the P generation?
b. What are the F1 genotypes and phenotypes?
Multiple Alleles: Blood Typing #3
If a man with blood Type-B, one of whose parents
had blood Type-O, marries a woman with blood
Type-AB.
a.
What percentage of their children should have
blood Type-B?
Multiple Alleles: Blood Typing #4
Both Mrs. Smith and Mrs. Jones had babies the same
day in the same hospital. Mrs. Smith took a baby girl
home, whom she named Shirley. Mrs. Jones took a
baby girl home, whom she named Jane. However, Mrs.
Jones began to suspect that her child had been
accidentally switched with the Smith baby in the nursery.
Blood tests were made: Mr. Smith was Type-A, Mrs.
Smith was Type-B, Mr. Jones was Type-A, Mrs. Jones
was Type-A. Shirley was Type-O and Jane was Type-B.
a. Did a mix-up occur?
b. Explain your answer.
Multiple Alleles: Blood Typing #5
A man with Type-O blood married a woman with
Type-AB get married. One of their children needs
an operation. This child has Type-B blood.
a.
b.
Can the child safely receive a blood transfusion
from either parent?
Explain your answer.
Genetic Disorders #1
Sickle cell anemia is inherited through an
autosomal recessive allele. People heterozygous
for sickle cell anemia are resistant to malaria.
Consider the offspring of two people who have the
genotype Aa.
a.
b.
What percentage of their offspring are likely to be
sickle cell sufferers?
What percentage of their offspring are likely to be
resistant to malaria and suffer few effects of the
disease?
Genetic Disorders #2
Huntington’s Disease is caused by an autosomal
dominant allele. A man with Huntington’s diseases
marries a woman who does not have the disease.
a.
b.
What is the probability that their children will also
have the disease?
Explain your answer.
Genetic Disorders #3
Phenylketonuria (PKU) is an autosomal genetic disease in
which the body cannot safely break down the amino acid
phenylalanine. If untreated, PKU causes severe brain
damage. To avoid this, people with PKU must eat a
special diet low in phenylalanine. Two people who have
normal phenotypes have a child. A blood test at birth
shows your child has PKU.
a. Is this disorder autosomal or sex-linked?
b. Explain your answer.
Genetic Disorders #3
Achondroplasia, a form of dwarfism, is caused by the
dominant allele A. Embryos with the genotype AA do not
survive. Suppose that two people with this form of
achondroplasia get married and have children.
a. What phenotypic ratio would you probably observe in
the children’s couple?
Genetic Disorders #4
One of the children from the previous problem with a
normal phenotype marries a person who also has a
normal phenotype.
a. What percentage of the children from this marriage are
likely to have achondroplasia?
Sex-linked #5
If a woman who is a carrier for a sex-linked disorder
already has one son who has the disorder, what is
the chance that if she has a second son he will also
have the disorder? Explain.
Sex-linked #6
If a man has a sex-linked disorder, what is the chance
that he will pass it on to one of his sons? Explain.
Sex-linked #7
If a man has a sex-linked disorder, what is the chance
that one of his daughters will be a carrier for that
disorder? Explain.
Sex-linked #8
If a man has a sex-linked disorder, what are the
chances that one of his grandsons will inherit that
disorder? Explain.
Sex-linked #8
If a man has a sex-linked disorder, what are the
chances that one of his grandsons will inherit that
disorder? Explain.
Sex-linked #9
It has been postulated that a condition known as
“hairy ears” is caused by a mutation of a gene on the
Y chromosome.
a. Assuming that this is true, what is the chance that one of
the sons of a man with hairy ears will inherit the “hairy-ear
mutation?” Explain.
b. What is the chance that one of the daughters of the man
referred to above will pass the “hairy-ear mutation” on to
one of her sons? Explain.