*2. In cats, blood type A results from an allele (I^A) that is dominant over an allele (i^B ) that produces blood type B. There is no O blood type. Shown below are the blood types of male and female cats that were mated and the blood types of their kittens. Give the most likely genotypes for the parents of each litter.

a. Blood type A_______ Blood type B___________4 kittens with blood type A, 3 with blood type B

b. Blood type B_______Blood type B __________ 6 kittens with blood type B

c. Blood type B_______Blood type A ___________8 kittens with blood type A

d. Blood type A_______Blood type A ___________7 kittens with blood type A, 2 kittens with type B

e. Blood type A_______Blood type A____________10 kittens with blood type A

f. Blood type A_______Blood type B ____________4 kittens with blood type A, 1 kitten with type B

*3. In humans, alkaptonuria is a metabolic disorder in which affected individuals produce black urine.
Alkaptonuria results from an allele (a) that is recessive to the allele for normal metabolism (A). Sally
has normal metabolism but her brother has alkaptonuria. Sally’s father has alkaptonuria and her
mother has normal metabolism.
a. Give the genotypes of Sally, her mother, her father, and her brother.

b. If Sally’s parents have another child, what is the probability that this child will have alkaptonuria?

c. If Sally marries a man with alkaptonuria, what is the probability that their first child will have
alkaptonuria?

**6. In cucumbers, dull fruit (D) is dominant to glossy fruit (d), orange fruit (R) is dominant to cream
fruit (r), and bitter cotyledons (B) is dominant to non-bitter cotyledons (b). The three characteristics
are encoded by genes located on different pairs of chromosomes. A plant homozygous for dull, orange
fruit and bitter cotyledons is crossed with a plant that has glossy, cream fruit and non-bitter cotyledons.
The F 1 are intercrossed to produce the F 2 .
a. Give the phenotypes and their expected proportions in the F 2 .

b. An F 1 plant is crossed with a plant that has glossy, cream fruit and non-bitter cotyledons. Give the
phenotypes and expected proportions among the progeny of this cross.

*7. In humans, ptosis (droopy eyelid) may be inherited as a dominant trait. Among 40 individuals who
are heterozygous for the ptosis allele, 13 have ptosis and 27 have normal eyelids.
a. What is the penetrance for ptosis?

b. If ptosis exhibited variable expressivity, what would this mean?

***10. Albinism is a recessive trait in humans. A geneticist studies a series of families in which both
these families must both be heterozygotes and that albinism should appear in 1 /4 of the children of
these families. To his surprise, the geneticist finds that the frequency of albinism among the children
of these families is considerably greater than 1 /4. There is no evidence that normal pigmentation
exhibits incomplete penetrance. Can you think of an explanation for the higher than expected fre-quency
of albinism among these families?

*2. Betty has red-green colorblindness, which is an X-linked recessive characteristic. Could Betty have inherited one of the genes for this disease from the following individuals (yes or no)?
                                   Yes or No
a. Her mother’s mother ________

*4. John and Cathy both have normal color vision. After ten years of marriage to John, Cathy gives
birth to a colorblind daughter. John files for divorce, claiming he is not the father of the child. Is John
justified in his claim of nonpaternity? Explain why.

*5. The Talmud, an ancient book of Jewish civil and religious laws, states that if a woman bears two sons who die of bleeding following circumcision (removal of the foreskin from the penis), any additional sons that she has should not be circumcised. (The bleeding most likely refers to the X-linked disorder hemophilia.) Furthermore, the Talmud states that the sons of her sisters must not be circumcised, whereas the sons of her brothers should. Is this religious law consistent with sound genetic principles? Explain your answer.

**6. Miniature wings in Drosophila melanogaster results from an X-linked gene ( m ) that is recessive to an allele for long wings ( m⁺). Sepia eyes is produced by an autosomal gene (s) that is recessive to an allele for red eyes (s⁺ ).

a. A female fly that has miniature wings and sepia eyes is crossed to a male that has normal wings and
is homozygous for red eyes. The F 1 are intercrossed to produce the F 2 . Give the phenotypes and their
proportions expected in the F₁ and F₂ flies from this cross.

Chapter 5  Extensions and Modifications of Basic Principles

*3. For each of the pedigrees (a, b, c, d, e) shown below, give the most likely mode of inheritance assum-ing
that the trait is rare. Carefully explain your reasoning.
This will hyperlink you to Chapter 6 Pedigree Analysis and Applications

b. A female fly that is homozygous for normal wings and has sepia eyes is crossed to a male that has

phenotypes and proportions expected in the F₁ and F₂ flies from this cross.