Name: ________________________
Date: __________________________
How are Traits on Sex Chromosomes Inherited
Hemophilia is a disorder in which the persons’ blood will not clot. The disorder
is inherited. If you have the dominant gene H, you will have normal blood. If you
have only the recessive gene h, your blood will not clot.
Color blindness is also a genetic disorder. In this disorder, the person does not
see certain colors, such as red and green. This person will see green as a grey color
and red as a yellow color. If you have at least one dominant gene B, you see all
colors. If you have only recessive genes, b , you cannot see red and green.
For each of the following problems, construct a Punnett square. Record your
answers in the space provided.
Problem 1:
Two parent have the following genes for hemophilia: XHXh and XHY. What type of
blood could their children have?
Children
Number of males
Number of females
Have normal clotting
____________________
______________________
Have hemophilia
____________________
________________________
Problem 2:
Two parents have the following genes for color blindness. XBXB and XbY. What
kind of color vision could their children have?
Children
Number of males
Number of females
Have normal vision
____________________
______________________
Have color blindness
____________________
________________________
Problem 3:
Two parents have the following genes for color blindness: XBXb and XbY. What
type of color vision could their children have?
Children
Number of males
Number of females
Have normal vision
____________________
______________________
Have color blindness
____________________
________________________
Questions:
1. What sex chromosomes do female offspring have? _____________________________
2. What sex chromosomes do male offspring have? ______________________________
3. How many genes do females have:
a. for blood clotting ________________
b. for color blindness _____________
4. How many genes do males have:
a. for blood clotting ________________
b. for color blindness _____________
5. Why is there a difference in the number of genes for blood clotting and color
blindness in males and females?
________________________________________________________________________________________
________________________________________________________________________________________
6. Which of the 2 traits studied in this activity are genetic disorders?
______________________________________________________________________________________
7. Look at problem 2. Hypothesize why there are no color-blind children even
though one of the parents is color blind?
______________________________________________________________________________________
______________________________________________________________________________________
8. Which of the parents give the trait of hemophilia to their son? Explain
why.
_______________________________________________________________________________________
_______________________________________________________________________________________
9.
Which of the parents give the trait of hemophilia to their daughter?
Explain why.
_______________________________________________________________________________________
_______________________________________________________________________________________