Name _____________________________________________
ActActivity:
Activity: Take a Class Survey
Goals:
 To develop a hypothesis concerning the occurrence of traits controlled by dominant
and recessive alleles.
 To determine if traits controlled by dominant alleles are more common than traits
controlled by recessive alleles.
 To interpret data about specific traits controlled by dominant and recessive alleles.
 To draw conclusions concerning the frequency and variation of the traits observed in
classmates.
Background Information:
Gregor Mendel was curious about the physical characteristics, or traits, of pea
plants. The passing of traits from parents to offspring is called heredity. Mendel’s work
was the foundation of genetics, the scientific study of heredity. .
From his work, Mendel reasoned that individual factors, one from each parent
controlled the inheritance of traits. Today, scientists call the factors that control traits
genes. The different forms of a gene are called alleles.
Individual alleles control the inheritance of traits. Some alleles are dominant,
while other alleles are recessive. A dominant allele is one whose trait always shows up
in the organism when the allele is present. A recessive allele is masked, or covered up,
whenever the dominant allele is present. A trait controlled by a recessive allele will only
show up if the organism inherits two recessive alleles for the trait.
Human traits are controlled by dominant and recessive alleles, causing many
different combinations of traits among a group of people. (Information is from Prentice
Hall: Science Explorer.)
Materials: mirror, data collection chart
Procedure:
Part 1: Dominant and Recessive Alleles
1. What I Know: Write a hypothesis that states whether you think certain traits
controlled by dominant alleles occur more often than traits controlled by recessive
alleles.
[Example: I predict that traits controlled by dominant alleles are (more common, less
common, equally as common) as traits controlled by recessive alleles.]
My hypothesis is:
2. See page 86 in your text book for pictures showing the following traits.
A. Free ear lobes vs. attached ear lobes
B. Hair on fingers vs. no hair on fingers
C. Widow’s peak vs. no widow’s peak
D. Curly hair vs. straight hair
E. Cleft chin vs. smooth chin
F. Smile dimples vs. no smile dimples
3. For each of the traits listed in the data table, determine which trait you have. Circle
that trait on your data table.
4. Each student will add their traits to a class data table on the white board. Count the
tally marks and record the number on your data sheet.
Dominant and Recessive Alleles
A. Circle your traits on the table below.
B. Record the class results from the white board onto the data table below.
Trait 1
Number
Trait 2
A
Free earlobes
Attached earlobes
B
Hair on fingers
No hair on fingers
C
Widow’s peak
No widow’s peak
D
Curly hair
Straight hair
E
Cleft chin
Smooth chin
F
Smile dimples
No smile dimples
Number
Part 2: Are You Unique?
1. Look at the Circle of Traits on page 87 in your text book. All the traits on your data
table appear in the circle.
2. Place the eraser end of your pencil or your finger on the trait in the small
central circle that applies to you - either free ear lobes or attached ear lobes.
2. Move your eraser onto the next description that applies to you. Continue using your
eraser to trace your traits until you reach a number on the outside rim of the circle.
3. You will share your number with your entire class to see how many of you share the
same numbers.
My number on the circle of traits: ____________
Questions:
1. The traits listed under “Trait 1” in the data table are controlled by dominant alleles.
The traits listed under “Trait 2” are controlled by recessive alleles.
Which traits controlled by dominant alleles were shown by a majority of students?
Were more dominant or recessive traits shown by students in the class?
2 If we increased the number of traits on the Circle of Traits from the five we observed
to say 15 or more, what would happen to the chance of someone in the class
sharing all the same combination of traits?
2. How does your data support the hypothesis you proposed in step 2?
Explain your answer with examples from this activity.