1. In guinea pigs, black fur color is controlled by a dominant allele (B) and brown by its recessive allele (b). 

Give the genotypes of the parents and offspring of a cross of a black male with a brown female that produces 

1/2 black offspring and 1/2 brown offspring. 

2. Albinism is a recessive trait that results in the absence of certain pigments in the hair, skin and eyes. The 

allele for albinism (c) is recessive to the allele for normal pigmentation (C).  A normally pigmented woman, 

whose father is an albino, marries an albino man whose parents are normal.  They have three children, two 

normal and one albino.  Give the genotypes for each person listed. 

3 . In petunias, a cross between red flowered plants (RR) and white flowered plants (rr) produce offspring with 

a pink color. Diagram such a cross using a Punnett square. 

a. If a red petunia plant is crossed with a pink plant, what kind of individuals would you expect to find and in 

what proportions? 

4. In garden peas, one pair of alleles controls the height of the plant and a second pair of alleles controls flower 

color.  The allele for tall (D) is dominant to the allele for dwarf (d), and the allele for purple (P) is dominant to 

the allele for white (p).  A tall purple crossed with a dwarf white produces all tall purple.  What is the genotype 

of the parents? 

5. In humans, normal skin pigmentation is influenced by an autosomal dominant gene (C), which allows 

pigmentation to develop. All individuals who are homozygous for the recessive allele (c) are unable to produce 

an enzyme needed for melanin formation and are therefore referred to as albino. Two normal parents produce an 

albino child. What are the chances that the next child will be an albino? 

6. Hemophilia is an X-linked recessive gene.  A normal woman whose father had hemophilia marries a normal 

man.  What are the chances of hemophilia in their children? 

7. Red-green color blindness is an X-linked recessive trait in humans. What is the probability that a color blind 

woman and a man with normal vision will have a color blind daughter? 

8. In humans, an X-linked disorder called coloboma iridia (a fissure in the iris) is a recessive trait.   

 A normal couple has an afflicted daughter.  The husband sues the wife for divorce on the grounds of infidelity 

(she cheated).  If you were the judge in this case would you be in his favor? 

9. Sherman has six toes and is albino. Having six toes is called polydactylism and is a dominant autosomal trait. Sherman is heterozygous for polydactylism. Albinism is a recessive autosomal trait. Sherman meets Sally who is heterozygous for both  albinism and polydactylism. Make a dihybrid (two-cross) Punnett Square showing the possible offspring Sherman and Sally might produce. List the genotypes and phenotypes. 

10. Make a pedigree chart of the following scenario: Gus and Suzie got married and had two girls (Abby and Rachel), and one boy (Sven). Gus and Suzie are both heterozygous for widows peaks. Abby and Rachel are heterozygous, and Sven does not have a widows peak. Abby marries Rex who does not have a widows peak. They have a girl and a boy. The boy has a widows peak, but the girl does not. Use page 203 of your textbook as a reference. Remember: Circles=girls, squares=boys. Shaded means they express the phenotype for widows peaks. 

Extra Credit Challenge!

11. Lisa and Ashton got married and had three girls, Cari, Mary, and Terry.   It was discovered that Lisa had 

muscular dystrophy.  Terry married Perry and had two boys, Pike and Tike. It was discovered that Terry 

and Pike had muscular dystrophy. Draw the Pedigree chart. *Remember* Muscular dystrophy is an X-linked recessive trait.