Download Lesson 3: How does children get traits that their parents do not have

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Lesson 3 & 4 Genetics
Lesson 3: How dochildren get traits that their parents do not have?
And how do traits skip a generation?
1. Do you know children who have traits that their biological parents do not have?
Have you ever heard of a trait that “skips a generation”?
In this lesson, we will explore these questions and find a model that can explain how this
happens.
2. Your teacher will show you a powerpoint to help you.
3. In the last lesson, you decided that the best model was the strong gene model.
In this lesson, your teacher will introduce you to two different “strong allele” models, and you
will try out the two models and see how they work.
One Allele Model – Each parent
contributes one allele, and the
“strongest” allele is the one that
determines what trait the children
have.
Two Allele Model – Each parent has
two alleles of their own, and each
gives one to the child. The strongest
allele in the pair determines what
trait the child will have.
4. Your teacher will walk you through a simulation using genetic boxes to help explain the two
models.
6. Below are four pieces of evidence. In pairs, read each piece of evidence.
7. Individually, complete the arrows diagram for Evidence 1 through 4. Discuss your arrows
with your partner. Give clear reasons to each other for your ideas, and discuss carefully any
arrows you disagree about.
Evidence
Evidence 1: Cats
Evidence 2: Skip a generation
Evidence 3: Shondra, Dan and Derrick
Evidence 4: Kumar Family
One Allele Model
Two Allele Model
8. Individually, answer this question: How is Evidence #2 related to the Two Allele Model
(supports, contradicts, etc.). Give reasons for your answer using details from the evidence.
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9. Individually, answer this question: How is Evidence #2 related to the One Allele Model
(supports, contradicts, etc.)? Give reasons for your answer using details from the evidence.
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10A. Discuss in your groups: Which model is better, based on the evidence so far. Give
detailed reasons for your ideas during your discussion (use model evaluation stems).
10B. Then answer the following questions.
Which evidence is the best evidence?
Which evidence supports or contradicts both models MOST STRONGLY?
Which evidence helps you the most to decide which model is better?
What is the best argument for the Two Gene Model?
What is the best argument for the One Gene Model?
11. Individually, answer this question. Which is the best “strong” allele model? Give 2 reasons
with detailed explanations using the evidence provided.
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LESSON 4 - DNA YARN ACTIVITY
Next we will use a physical model made of yarn on a popsicle stick to show how the two-gene model works.
You will also learn these important terms in genetics: DNA, gene, allele, and chromosome.
Our goal is to learn how to use these terms when talking about adults and their children.
Step 1: Tie together the different length pieces of the colored yarn. The strings will be different lengths, this is
o.k. Tie them together in this order:
Brown – Purple – Green – Yellow – Red – Blue
Step 2: After you have tied the pieces of yarn together, tape one end of the piece of yarn to one end of the
Popsicle stick.
Step 3: Wrap the yarn around the Popsicle stick.
Step 4: Tape the other end of yarn to the popsicle stick.
Step 5: Repeat steps 1 – 4 for the other popsicle stick.
Below is the table of traits showing the color of the wool and whether it is dominant or recessive.
Wool Color
Trait
Dominant
Dark brown
Dimples
Light brown
No Dimples
Dark purple
Unattached Earlobes
Light purple
Attached Earlobes
Dark green
Widow's Peak
Light green
Straight Hairline
Dark yellow
Straight Thumb
Light yellow
Curved Thumb
Dark red
Can Roll Tongue
Light red
Can't Roll Tongue
Dark blue
Can Taste PTC
Light blue
Can't Taste PTC
Recessive
X
X
X
X
X
X
X
X
X
X
X
X
1. Humans have 46 chromosomes. These come in pairs of 2, so there are 23 pairs of chromosomes. The
information for each trait can be found on a pair of chromosomes. Now that we have 2 chromosomes with
multiple alleles (different shades of yarn) we can figure out the traits for this adult. Fill in the table below for
your traits. Your teacher will put an example on the board to help you fill in the table.
Wool Color on
Chromosomes - write
whether it is light or dark
Individuals Genotype write whether it is
dominant or recessive
Brown
/
/
Purple
/
/
Green
/
/
Yellow
/
/
Red
/
/
Blue
/
/
Individuals
Phenotype - write in
their trait
2. With your partner, each person should randomly pick one chromosome from the pair that they made. Set
the other chromosome off to the side, it will not be used. Now pair your remaining chromosome with your
partner. Make sure it is not the one you set off to the side. This new pair of chromosomes is one possible child
who gets half their DNA from one parent and half their DNA from the other parent.
3. For this new individual fill in the table below for your traits.
Wool Color on
Chromosomes - write
whether it is light or dark
Individuals Genotype write whether it is
dominant or recessive
Brown
/
/
Purple
/
/
Green
/
/
Yellow
/
/
Red
/
/
Blue
/
/
Individuals
Phenotype - write in
their trait
Just in case you need it we have included the trait below to help you out.
Wool Color
Trait
Dark brown
Dimples
Light brown
No Dimples
Dark purple
Unattached Earlobes
Light purple
Attached Earlobes
Dark green
Widow's Peak
Light green
Straight Hairline
Dark yellow
Straight Thumb
Light yellow
Curved Thumb
Dark red
Can Roll Tongue
Light red
Can't Roll Tongue
Dark blue
Can Taste PTC
Light blue
Can't Taste PTC
Dominant
Recessive
X
X
X
X
X
X
X
X
X
X
X
X