Name: ______Date: ______Per. ______

Pedigree & Human Genetic Practice Worksheet

  1. The following pedigree illustrates the inheritance of a recessive trait. Identify the genotypes of each individual shown in the pedigree.

Key: ______

  1. The following pedigree illustrates the inheritance of a dominant trait. Identify the genotypes of each individual shown in the pedigree.

Key: ______

  1. Examine the pedigree below showing the inheritance of albinism. Identify the genotypes of all individuals

a.  Key: ______

b.  If individual E marries a man with albinism, what is the probability they would have a child with the disorder? Cross: ______

c.  If this same couple (E x albino male) has a child with normal pigmentation, what is the probability their child is a carrier for albinism? ______

  1. Two couples, the Pages and the Bakers, had baby boys in the same hospital at the same time. There was mix up in the nursery. Do Punnett squares to determine the biological parents of the babies. Us the information given below to help you.

Name: Mrs. Page Mr. Page Mrs. Baker Mr. Baker Baby #1 Baby #2

Blood Type: B AB B A A O

Baby #1 Belongs to the ______Baby #2 Belongs to the ______

Sex-Linked

  1. A hemophiliac man marries a woman who is a carrier of the hemophiliac condition. Draw a Punnett square representing the offspring of this marriage.

a.  What percentage of the offspring will be a hemophiliac? ______

b.  Is it possible for these parents to produce an offspring that is neither a carrier nor a hemophiliac? ______

c.  If so, would this individual be male of female? ______

d.  What would be the genotype of this individual? ______

e.  Is it possible to have a female hemophiliac? ______

  1. In the case of the sex-linked gene responsible for hemophilia, a hemophiliac father never transmits hemophilia to his son. Explain why: ______

______

  1. Red-green color blindness is also a sex-linked recessive trait in humans. Using B as the superscript for normal vision and b for color blindness, give the genotypes for the following:

a.  A normal female:______d. A normal male: ______

b.  A carrier female: ______e. A color blind male: ______

c.  A color blind female: ______

  1. In the following problems, draw Punnett squares to represent the crosses. Give the proportion (1/4, 2/4 ect.) of each phenotype listed. Note….. some phenotypes may not appear so you may leave those blank.

a.  A color blind male x a female carrier

Normal female (not carrier) ______Color blind female ______

Carrier ______

Normal male ______

Color blind male ______

b.  Normal vision male x color blind female:

Normal female (not carrier) ______Color blind female ______

Carrier ______

Normal male ______

Color blind male ______

c.  Color blind male x normal female (not a carrier):

Normal female (not carrier) ______Color blind female ______

Carrier ______

Normal male ______

Color blind male ______

  1. Can a normal blood clotting man & a carrier female have a hemophilic son? ______
  2. Why? ______

Complete the following autosomal crosses:

  1. Is Huntington’s dominant or recessive? ______
  1. What is the probability of a male heterozygous for Huntington’s and a homozygous recessive female having a child with Huntington’s?

a.  Phenotypic ratio: ______

b.  Genotypic ratio: ______

  1. The following pedigree shows the path of inheritance of hemophilia through several generations. Identify the genotypes of each individual.

a.  Key: ______

Identify the genotypes of all the individuals in the pedigree.

If individual III-2 marries an unaffected woman whose dad had hemophilia, what is the probability that their son will be

hemophilic? ______What about their daughter? ______Show your work using a Punnett square!

If individual III-3 marries a non-hemophilic male, what is the probability that they will have hemophilic daughters? _____ sons? _____

Show your work using a Punnett square!

  1. Fragile-X syndrome is a recessive sex-linked disorder located on the X chromosome. Below is a pedigree tracing the passing of the fragile-X syndrome gene through 3 generations. Write in the genotypes on the line next to /blow each individual.
  1. Below is a recessive sex-linked pedigree tracing the red-green colorblindness gene located on the X chromosome. Write in the genotypes on the line next to/below each individual.

  1. A person with type A blood (unknown genotype) marries a person with type O blood. What blood types are possible among their children. (Show 2 crosses)

______

  1. Two people with type O blood have three children. How many of those three children also have type O blood? ______
  1. Write in the genotypes on the line next to/below each individual.

Tracing the path of an autosomal dominant trait

Trait: Neurofibromatosis

Forms of the trait:

ñ  The dominant form is neurofibromatosis, caused by the production of an abnormal form of the protein neurofibromin. Affected individuals show spots of abnormal skin pigmentation and non-cancerous tumors that can interfere with the nervous system and cause blindness. Some tumors can convert to a cancerous form.

ñ  The recessive form is a normal protein - in other words, no neurofibromatosis.

A typical pedigree for a family that carries neurofibromatosis is shown below. Use the letter "N" to indicate the dominant neurofibromatosis allele, and the letter "n" for the normal allele.