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Inherited Traits
BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN
Grade 4—Quarter 3
Activity 25
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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.
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The student knows that to compare and contrast observations and results is an essential
skill in science.
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The student knows that a model of something is different from the real thing, but can be
used to learn something about the real thing.
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SC. H.2.2.1
The student knows that natural events are often predictable and logical.
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. Remind students that they made a model of a chromosome in this activity. Ask, Why did
you use a model and not the real thing? (Answers will vary; models are used when the real
objects are too small, too big, too hard to obtain, or events take too long to occur; they
are also used to help us visualize something we cannot see.) Do we also need models to
understand how a human cell works? (Yes, the cell and its parts are too small to see.)
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2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the
activity.
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activity 25 Inherited Traits
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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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Inherited Traits
OBJECTIVES
In this activity, students learn about
dominant and recessive genes and how they
express themselves in physical traits.
The students
learn the difference between dominant and
recessive genes
use a model to explore how genes are
passed from parent to offspring
infer the traits of offspring based on the
makeup of their gene pairs
PREPARATION
1
Make a copy of Activity Sheet 25, Part A,
for each student. Make a copy of Activity
Sheet 25, Part B, for each group.
2
Cut four light-colored and four darkcolored pipe cleaners into four equal
pieces each to make 16 short light and 16
short dark pipe cleaners.
3
Divide the bag of beads up so that each
group of students gets three round and one
square bead of the same color. (It doesn’t
matter if two teams use the same color.)
BACKGROUND INFORMATION
SCHEDULE
About 40 minutes
VOCABULARY
chromosome
dominant gene
recessive gene
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MATERIALS
For each student
1
Activity Sheet 25, Part A
1 box crayons*
For each group of four
1
1
3
2
2
Activity Sheet 25, Part B
bead, square (same color as round
beads)
beads, round, same color
pipe cleaners, short, dark-colored
pipe cleaners, short, light-colored
*provided by the teacher
Chromosomes are tiny structures found in the
nucleus of a cell. Each human cell contains a
set of 46 chromosomes, one pair each of 23
different chromosomes. Each chromosome
carries many genes, which code for traits.
Genes for all of an individual’s traits are found
on these 23 pairs of chromosomes. An
individual gets one chromosome of every pair
from each parent.
Many traits are determined by a single pair of
genes. When both genes for the trait are the
same, such as for brown eyes, the individual
has brown eyes. When both genes are for
blue eyes, the individual has blue eyes. But
what happens if an individual has one gene
for brown eyes and one gene for blue eyes?
The gene for brown eyes masks the gene for
blue eyes, and the individual has brown eyes.
The blue-eyed trait is not expressed. The gene
that masks the other and is expressed is called
a dominant gene. The gene that is masked and
not expressed is a recessive gene. Thus, brown
eye color is a dominant trait, and blue eye
color is a recessive trait. Brown-eyed
individuals can have either two identical genes
for brown eye color or one gene for brown and
one gene for blue. These two individuals are
indistinguishable externally. Only one
combination of genes (blue/blue) will cause
someone to have blue eyes.
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Activity Sheet 25, Part A
Inherited Traits
Activity Sheet 25, Part B
Inherited Traits
Key
1. Use crayons to draw the pipe-cleaner-and-bead chromosome models for the
mother and the father in the boxes below.
Dominant gene:
2. Then draw the chromosome models for each child they “made.”
Recessive gene:
Mother
Father
Child 1
Child 2
Mother’s Chromosomes
Father’s Chromosomes
Child’s Chromosomes
Can Child 1 roll his or her tongue? Explain?
Answers will depend on whether or not the child has the dominant gene from
the father. If the child has the gene, he will be able to roll his tongue.
Can Child 2 roll his or her tongue? Explain?
Answers will depend on whether or not the child has the dominant gene from
the father. If the child has the gene, she will be able to roll her tongue.
1
Have students try to curl the two sides of
their tongue toward the roof of their mouth.
This trait is called tongue rolling. (See Figure
25–1.) Tell students not to be upset if they
cannot roll their tongue. Some people can do
it, and some people cannot.
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Figure 25-1. Tongue rolling and non-tongue rolling traits.
activity 25 Inherited Traits
Additional Information
If students cannot tell if they are rolling their
tongue, have them ask a classmate.
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Guiding the Activity
Guiding the Activity
2
Additional Information
Remind students that genes are tiny
structures in cells that determine traits.
Children inherit genes from their parents.
Write the term chromosome on the board. Tell
students that genes are carried on structures
called chromosomes. Chromosomes come in
pairs. So genes also come in pairs. One gene
for a trait is found on one chromosome of a
pair, and the other gene for the same trait is
found on the other chromosome of the pair.
You inherit one chromosome of each pair
from each parent.
You may choose to draw a pair of
chromosomes on the board and mark the
location of a gene pair on each. (See Figure
25-2.)
Gene A
Gene A
Tell students that tongue rolling, like many
other traits, is controlled by genes. Children
who inherit a gene for tongue rolling from
both parents are able to roll their tongues.
Children who inherit a gene for not being able
to roll their tongues from each parent will not
be able to roll their tongues, no matter how
hard they try.
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3
Ask, What do you think happens when a
child inherits a gene for being able to roll
her tongue from her mother and a gene for
not being able to roll her tongue from her
father?
Figure 25-2. A pair of genes on a pair of chromosomes.
Answers will vary. Encourage discussion.
Write the terms dominant gene and recessive
gene on the board. Explain that some genes
are dominant, or powerful. Other genes are
recessive, or weak. When a dominant gene is
in a pair with a recessive gene, the dominant
gene is the one that comes through.
In the case of tongue rolling, the gene for
being able to roll the tongue dominates, or
overpowers, the gene for not being able to
roll the tongue. So, a person with one gene
for tongue rolling and one gene for nontongue rolling will be able to roll his or her
tongue.
Recessive traits are only seen when both
genes in the pair are recessive. In the case of
tongue rolling, only a person with two
recessive genes for tongue-rolling will not be
able to roll his tongue.
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Guiding the Activity
4
Additional Information
Tell students that they will now create
chromosome models that they can use to
look at how different pairs of genes can be
passed from parents to offspring.
Hold up a pipe cleaner with a bead on it.
Explain that, in this model, the pipe cleaner
will represent a chromosome and the bead
will represent a gene on that chromosome.
Dark pipe cleaners will represent
chromosomes from the father. Light pipe
cleaners will represent chromosomes from
the mother. Square beads will represent
dominant genes. Round beads will represent
recessive genes.
5
Write this key on the board so that students
can refer to it as needed.
Distribute Activity Sheet 25, Part A, and a
box of crayons to each student. Distribute
pipe cleaners, beads, and Activity Sheet 25,
Part B, to each group of four.
Have students use the pipe cleaners and
beads to make a pair of chromosomes for a
mother with two recessive tongue-rolling
genes as follows: place a round bead on one
light-colored pipe cleaner and another round
bead on another light-colored pipe cleaner.
Fold over the ends of the pipe cleaners once
the beads are on.
Safety Note: Tell students to handle the
pipe cleaners carefully. The ends may be
sharp.
Now have students make a chromosome pair
for a father with one dominant tongue-rolling
gene and one recessive tongue-rolling gene
by putting one round bead on a dark-colored
pipe cleaner and one square bead on another
dark-colored pipe cleaner.
Have students place these chromosomes in
the Father’s Chromosomes box on Activity
Sheet 25, Part B.
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Have students place this chromosome pair in
the Mother’s Chromosomes box on Activity
Sheet 25, Part B.
Guiding the Activity
6
Additional Information
Invite one student in each group to close his
or her eyes and randomly choose one
chromosome from the mother and one from
the father and place them in the Child’s
Chromosomes box on Activity Sheet 25, Part B.
Ask, What does this new chromosome pair
represent?
It represents one pair of chromosomes in a
cell of the child. Remind students that
chromosomes exist in pairs within the cells in
their body. One chromosome comes from the
mother and one from the father.
Ask, Are any dominant genes present in the
child’s chromosomes?
Answers will vary depending on which of the
father’s chromosomes was chosen.
Ask, Can this child roll his or her tongue?
How can you tell?
The child can roll his or her tongue if
students have chosen the chromosome from
the father that has a square (dominant) bead.
If students have chosen the chromosome
with a round (recessive) bead, the child will
not be able to roll his or her tongue.
Have students record the results of this
exercise on Activity Sheet 25, Part A.
7
Tell students to put the child’s chromosomes
back into the boxes for the mother and
father.
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Now, have them imagine that these parents
have another child. Invite a second volunteer
to close his or her eyes and randomly choose
another chromosome from each parent and
place the two chromosomes in the Child’s
Chromosome box.
Ask, Will this child be a tongue roller? How
can you tell?
The child can roll his or her tongue if
students have chosen the chromosome from
the father that has a square (dominant) bead.
If students have chosen the chromosome
with a round (recessive) bead, the child will
not be able to roll his or her tongue.
Have students record the results of this
exercise on Activity Sheet 25, Part A.
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Have students repeat Steps 5–7, making
chromosomes for two tongue-rolling parents
with one dominant gene and one recessive
gene. If students choose the chromosome
with the recessive gene from each parent,
they will discover why children often have
traits that neither parent has.
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SCIENCE JOURNALS
Have students place their completed
activity sheets in their science journals.
CLEANUP
Have students take apart their model
chromosomes and place the beads and
pipe cleaners back in the kit.
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REINFORCEMENT
Connections
Science Extension
Science and Language Arts
Students might enjoy finding out how many
chromosomes are in the body cells of other
species besides humans. Encourage them to
research a wide variety of organisms—
protists, plants, invertebrates, fish,
amphibians, reptiles, birds, and other
mammals, including our closest evolutionary
relative, the chimpanzee.
Ask students to research the derivation and
origin of the word chromosome. (from the
Greek chromo, “color,” and some, “body”) To
be visible with a microscope, chromosomes
must be stained with a colorful dye, thus
giving rise to the term “colored body.”
Science Challenge
Tell students that an adult human body
contains about ten trillion cells. Ask students
to write this number. (10 followed by 12
zeros). Now, tell students that human cells
have 46 chromosomes. Ask them to calculate
the total number of chromosomes in an adult
human body. (10,000,000,000,000 cells × 46
chromosomes = 460,000,000,000,000
chromosomes)
Have students make a list of some human
traits that are inherited, then do library or
Internet research to determine on what
chromosome the gene that controls each trait
is located. As students do research, they will
discover that not all traits are controlled by a
single gene. For example, skin color and
height are determined by many genes. Also,
some traits are determined by genes that
blend together to form a new trait. For
example, a person who has a gene for
straight hair and a gene for curly hair will
have wavy hair. Tell students to concentrate
on finding out the locations of genes of
simple traits that they have studied.
Science and Math
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Science and the Arts
Many life science and biology textbooks
published in recent years contain dramatic
photographs of chromosomes, especially
those that have been dyed with fluorescent
dyes. In addition, some professional artists
have created art based on structures such as
chromosomes. Have students look through
books to find such photographs and
illustrations.
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activity 25 Inherited Traits