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?

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 #4

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. Can the child safely receive a blood transfusion from either parent?

b. 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. What percentage of their offspring are likely to be sickle cell sufferers?

b. 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. What is the probability that their children will also have the disease?

b. Explain your answer.

Genetic Disorders #3Phenylketonuria (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.