Name: _____________________________ Period: ______
Genetics: X Linked Genes & Pedigrees
****In fruit flies, eye color is a sex linked trait. Red is dominant to white ****
1. What are the sexes and eye colors of flies with the following genotypes:
X R X r ______________________ X R Y ______________________ X r X r ______________________
X R X R ______________________ X r Y ______________________
2. What are the genotypes of these flies:
white eyed, male _____________ red eyed female (heterozygous) ________
white eyed, female ___________
red eyed, male ___________
3. Show the cross of a white eyed female X r X r with a red-eyed male X R Y in the Punnett Square
below.
Phenotypes: ___________________________________________________________________
4. Show a cross between a pure red eyed female and a white eyed male in the Punnett Square below.
What are the genotypes of the parents?
___________& _______________
How many are:
white eyed, male ____
red eyed, male ____
white eyed, female ____
red eyed, female ____
5. Show the cross of a red eyed female (heterozygous) and a red eyed male.
What are the genotypes of the parents?___________ & ________________
How many are:
white eyed, male____
red eyed, male ____
white eyed, female ___
red eyed, female ____
6. In humans, hemophilia is a sex linked trait. Females can be normal (X H X H), carriers (X H X h), or have
the disease (X h X h).
Males will either have the disease (X h Y)or not (X H Y); but they won’t ever be carriers
__________ = female, normal
__________ = male, normal
__________ = female, carrier
__________ = male, hemophiliac
__________ = female, hemophiliac
Show the cross of a man who has hemophilia with a woman who is a carrier in the Punnett Square
below.
What is the probability that their children will have the disease? __________
7. A woman who is a carrier marries a normal man. Show the cross in the Punnett Square below.
What is the probability that their children will have hemophilia? ___________
What sex will a child in the family with hemophilia be? ________________
Autosomal Pedigree Chart
Background information: Pedigree charts are used to trace a gene as it is passed down from
generation to generation. The squares represent a male and the circles a female. In the example
below, the shaded circles and squares will represent having the disorder. Make sure to read each
question to find out if a disorder is caused by dominant alleles or recessive alleles. A person can be a
carrier of a trait, meaning they will have heterozygous alleles.
8. Cystic fibrosis is an autosomal recessive disease where mucus develops in the lungs, liver, and the
pancreas. Below is an autosomal pedigree chart tracing the passing of the cystic fibrosis gene through
three generations. Write the genotypes on the lines next to/below each individual.
Answer the following questions using the autosomal pedigree chart above:
a. What is the phenotype of individual # 2? ____________________________________
b. What is the phenotype of individual # 3? ____________________________________
c. What is the phenotype of individual # 5? ____________________________________
d. What is the phenotype of individual # 7? ____________________________________
e. What is the phenotype of individual #10? ____________________________________
f. What is the phenotype of individual #11? ____________________________________
g. Why did individuals 9, 11, and 12 get the disorder when their parents did not have the
disorder? ___________________________________________________________________
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