Download Sex-Linked Pennies Lab - St. Edwards University

Name:_____________________ Date:________Pd:____
Sex-Linked Traits: Flipping Over Color Blindness
The sex chromosomes of a female are XX, and those of a male are XY. Traits
controlled by genes located on the sex chromosomes are called sex-linked traits.
Red-green color blindness, an inability to distinguish the color red from the color
green, is a recessive sex-linked trait. A male needs only one recessive sex-linked
gene to express color blindness. A female must have two recessive genes to show
the trait. In this activity you will use coins to demonstrate color blindness in a
family.
Materials
Two pennies; Masking tape; Pen
Activity
1. Select one of the pennies to represent the male parent. Place a piece of tape
on both sides of the penny. On one side of the penny write Xc. On the other
side write Y. This is Paul, and he is color-blind.
2. Place tape on each side of the second penny. On one side of the penny write
Xc and on the other side write XC. This is Jane, and she has normal vision
but carries the gene for color blindness.
3. Paul and Jane marry and begin to raise a family. Toss the two pennies and
allow them to land on the table. The combination of traits shown on the
coins represents the traits of their first child. Was the first child a boy or
girl? Was the child color-blind? Record your result.
4. Flip the coins seven more times and record your results.
BOY or GIRL
Colorblind - Y/N
Write the Alleles
1
2
3
4
5
6
7
8
1. How many boys and girls did Paul and Jane have?
2. How many of the children were color-blind, and how many had
normal vision?
3. Do you think color blindness is more common in boys or girls? Why?
4. What does this tell you about color blindness and how this relates to
genes?