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26 Traits and More Traits
BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN
Grade 4—Quarter 3
Activity 26
SC.F.1.2.3
The students knows that living things are different but share similar structures.
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The student knows that many characteristics of an organism are inherited from the parents
of the organism, but that other characteristics are learned from an individual’s interactions
with the environment.
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The student knows that a successful method to explore the natural world is to observe and
record, and then analyze and communicate the results.
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The student knows that to work collaboratively, all team members should be free to reach,
explain, and justify their own individual conclusions.
SC.H.1.2.4
The student knows that to compare and contrast observations and results is an essential
skill in science.
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ACTIVITY ASSESSMENT OPPORTUNITIES
The following suggestions are intended to help identify major concepts covered in the activity
that may need extra reinforcement. The goal is to provide opportunities to assess student
progress without creating the need for a separate, formal assessment session (or activity) for
each of the 40 hands-on activities at this grade level.
1. Tell students that the more they look at their inherited traits, the more they should see
how unique they are. Have students write a one page “biography” about themselves. The
biography should include all the traits they identified in this activity. Remind students that
these must be inherited traits, not “learned” behavior, or a practiced skill. (Evaluate
responses based on creativity, but be sure students stay with inherited traits and do not
describe a skill they can practice and improve upon.)
2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the
activity.
In addition to the above assessment suggestions, the questions in bold and tasks that
students perform throughout the activity provide opportunities to identify areas that may
require additional review before proceeding further with the activity.
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activity 26 Traits and More Traits
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26 Traits and More Traits
OBJECTIVES
Students observe a variety of physical traits
and determine the gene combinations
needed to express those traits.
The students
observe six of their physical traits
determine what combination of genes are
needed to express each trait
observe and compare the physical traits of
their classmates
recognize that each person is unique
because no two people have exactly the
same set of traits
SCHEDULE
About 30 minutes
MATERIALS
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For each student
1
Activity Sheet 26, Parts A and B
1
mirror, hand*
*provided by the teacher
PREPARATION
1
Make a copy of Activity Sheet 26, Parts A
and B, for each student.
2
Collect and distribute hand mirrors if they
are available.
BACKGROUND INFORMATION
In this activity, students look at traits that
show complete dominance. That is, one gene
is completely dominant to another and the
recessive gene is not expressed.
But, in general, inheritance in humans is
much more complex. Relatively few traits are
determined by only a single gene. Sometimes
a dominant and a recessive gene together
produce a blended trait instead of the
dominant gene masking the recessive gene.
For example, blending occurs when a gene for
straight hair is paired with a gene for curly
hair. The combination results in the individual
having wavy hair.
With still other traits, more than two genes
are involved. For example, having brown eyes
seems to be dominant to having blue eyes,
but some people have hazel or green eyes,
and there are many shades of brown. So
many possibilities exist because eye color is
determined by combinations of many genes.
What happens when you begin to look at
more than one trait in people? The many
possible variations in an individual’s
thousands of traits offer so many possible
combinations that no two people will have the
same combination. Each person is unique.
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Activity Sheet 26, Part A
Traits and More Traits
Activity Sheet 26, Part B
Traits and More Traits
Key
Record a different student’s name in each column. Begin with yourself.
Write a D or an R for each trait according to your observations and the
pictures shown on Activity Sheet 26, Part A.
D = dominant gene
R = recessive gene
Me
Trait
Little finger bent
or straight?
R No freckles
D Freckles
D Turned-up nose
R Straight nose
Student 1
Student 2
Answers will vary.
Hair or no hair on
middle of finger?
Nose turned up
or straight?
Freckles or no
freckles?
Tongue folds back
or doesn’t fold?
D No tongue folding
Ear point or no
ear point?
R Tongue folding
Record the gene pair combinations that results in each of the traits you
show by writing a D for a dominant gene and an R for a recessive gene.
Possible combinations include DD, DR, and RR. If more than one gene
combination is possible for a trait, record all possible combinations.
D Straight little finger
R Bent little finger
Little finger
bent or
straight?
Hair or no
hair on
middle of
finger?
Nose turned
Freckles or
up or
no freckles?
straight?
Tongue
folds back
or doesn’t
fold?
Ear point
or no
ear point?
Answers will vary.
D Hair on middle finger
R No hair on middle finger
D Ear point
R No ear point
Guiding the Activity
Distribute a copy of Activity Sheet 26, Part A,
to each student. Have students look at the
pictures of inherited traits on the activity
sheet. (See Figure 26–1.) Describe each trait.
If possible, find someone in the class who
shows each trait so that all students can
observe the traits firsthand.
Tell students that the D in the pictures stands
for a dominant trait, and the R stands for a
recessive trait. Ask, What gene pair must
you have to show a trait that is marked D
in the pictures?
To show a dominant trait, you must have at
least one dominant gene in the pair that
controls that trait. The other gene of the pair
can be either dominant or recessive.
Remind students that they inherited one gene
of each pair from their mother, and one from
their father.
Ask, What gene pair must you have to show
a trait that is marked R in the pictures?
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activity 26 Traits and More Traits
To show a recessive trait, you must have two
recessive genes in the pair that controls that
trait.
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1
Additional Information
R No freckles
D Freckles
D No tongue folding
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D Straight little finger
D Hair on middle finger
R No hair on middle finger
D Turned-up nose
R Straight nose
R Tongue folding
R Bent little finger
D Ear point
R No ear point
Figure 26-1. Some dominant and recessive traits.
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Guiding the Activity
3
4
5
Distribute a copy of Activity Sheet 26, Part B,
to each student. Tell them that they are going
to observe and record six of their own traits
on the first chart. Then they will determine
what genes they have that determine those
traits.
Have students decide which version of each
trait they show and record either a D or an R
for each trait in the Me column of the first
chart. Remind them that an R represents a
recessive trait and a D represents a dominant
trait.
Students should use Activity Sheet 26, Part A,
for reference. Have hand mirrors available if
students need them to observe their traits.
Have students record the gene pair that is
responsible for each of the traits they show in
the second chart. If more than one gene
combination is possible, they should record
all possible combinations.
Students should record both DD and DR if
they show a dominant trait. They should
record RR if they show a recessive trait.
Ask, What gene combination represents a
recessive trait?
Two R genes represent a recessive trait.
Ask, What gene combination represents a
dominant trait?
Either DD or DR genes can represent a
dominant trait.
Ask, Can you be sure what genes you have
if you show a dominant trait? Explain.
No. You know only that you have at least one
D gene.
Now have each student choose two
classmates and record their initials under
Student 1 and Student 2 in the first chart.
Have students observe the first trait, bent or
straight little fingers, in their two classmates
and record either a D or R for the trait.
You may prefer to assign students into
groups of three.
Ask, Are your two classmates like you in
this trait?
Answers will vary.
Have students observe the remaining five
traits in their two classmates and record
either a D or R for each trait. After they
observe each trait, ask again if their two
classmates are like them in this trait.
When they have finished observing all six
traits, ask, What is happening to the
number of students with the same set of
traits as you?
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activity 26 Traits and More Traits
Students should notice that as more traits are
observed, fewer students have all the traits in
common.
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2
Additional Information
Guiding the Activity
6
Tell students that they have thousands of
traits, although they have observed only six
of them. Ask, If you could observe all your
thousands of traits, do you think anyone in
your class would match all the same traits
as you?
REINFORCEMENT
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Have students consider the traits of a
relative, such as a sister or brother, and the
traits of their best friend. Have them
determine who has more matching traits to
theirs. Have students suggest a reason why.
Additional Information
Students should suggest that when all traits
are considered, there are too many possible
combinations for any two people to have the
same traits and the same set of genes.
SCIENCE JOURNALS
Have students place their completed
activity sheets in their science journals.
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Connections
Science Extension
Science and Math
Suggest that students work in small groups
to write rap songs about traits, using
concepts and terms they have learned so far.
Let each group find or create recorded
musical accompaniment for its song and then
perform it. If students have access to a video
camera, they might prefer making a video
rather than performing live.
Have students choose a trait such as eye
color, and count the number of students in
the class who have each eye color. Have
students calculate the percentage of students
in the class with each eye color. Guide them
in this activity by telling them to divide the
number of students with each eye color by
the total number of students in the class and
multiply the answer by 100. Then, ask each
student to construct a pie chart showing the
distribution of eye colors.
Invite a statistician to visit the class and ask
him or her to explain in simple terms why it is
not likely that any two people will have all
their traits in common. Ask the visitor to
introduce a discussion of probability by using
the tossing of first one coin and then several
coins.
Science and the Arts
Suggest that each student or group create a
collage showing the many variations that
occur in one particular feature, such as the
nose or eyes. Students can cut pictures from
magazines and newspapers or photocopy
pictures in books. Create a classroom display
of students’ collages.
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activity 26 Traits and More Traits
Science, Technology, and Society
Explain that a wide variety of skin colors are
produced by only a few genes. Like skin color,
color photographs in books and magazines
are produced with only four colors of ink.
Have students examine color photographs
with a magnifier, identify the four colors
(magenta, yellow, blue, and black), and
observe how the number of dots of each color
and their placement create the “full-color”
image we see from a distance.
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Science and Careers