HOW COMMON ARE TONGUE-ROLLERS?
INTRODUCTION
Can you roll your tongue? Do your fingers have mid-digital hair? Do you have a
widow’s peak? These three traits are known to be inherited in humans. Every
human being has 46 chromosomes. Each chromosome contains thousands of
genes. Although we do not know the function of all of these genes, there are a few
genes that produce easily identifiable traits such as the widow’s peak. In this lab
you will study the three traits mentioned above.
THE TRAITS
The ability to roll your tongue is dominant to the inability
to roll your tongue. Are you a roller?
The presence of mid-digital hair is dominant to the absence
of mid-digital hair. Look at your fingers. Notice that each
finger has three segments. All humans have hair on the
backs of their fingers on the segment nearest the palm.
However, some people also have hair on the middle segment.
Do you have mid-digital hair?
The presence of a widow’s peak is dominant to the absence
of a widow’s peak. If your hair comes to a peak in the
middle of your forehead, you have a widow’s peak. Do you
have a widow’s peak?
PROCEDURE
1.
2.
3.
4.
5.
6.
7.
Try to roll your tongue. Are you a roller or non-roller?
Record your tongue-rolling trait in the data table.
Gather tongue-rolling data for the class.
Record the class data in the data table.
Calculate the percent of tongue-rollers versus non-tongue-rollers.
Repeat this procedure for mid-digital hair and widow’s peak.
Complete the analysis questions.
DATA
dominant
trait
tongueroller
mid-digital
hair
widow’s
peak
recessive
trait
non-tongue
roller
lack middigital hair
lack widow’s
peak
my trait
dominant
number
recessive
number
dominant
percent
recessive
percent
ANALYSIS
1. For which traits do the majority of students display the dominant trait?
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2. For which traits do the majority of students display the recessive trait?
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3. Nationally, about 70% of the population are tongue-rollers and about 30% are
non-tongue-rollers.
a. How does the class data compare to the national figures?
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b. Discuss reasons for possible differences between the class and the
national data.
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4. Do dominant traits always occur in a majority of people?
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Explain. _______________________________________________________________
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