Download Lesson 2: Testing Inheritance Models

Name: ____________________________
Date: ____________
Period: ________
Lesson 2: Testing Inheritance Models
Directions:
1.​ Here are two models of how children inherit their traits from their parents. These models
were proposed by students at your school. Read each model in pairs. With your partner,
discuss which model is better. ​ ​Circle which model you think is better, and discuss reasons
why you think one is better than the
​ other​
​
or why they are equally good or bad.
Model A: Strong Parent
Children will get all of their traits and things
from the parent with the stronger trait. So
a mother whose traits are stronger will give
all of her genes to her son.
Model B: Sex Model
Girls get traits from their moms and boys
get traits from their dads.
Humans vary in their traits. Here are some examples of these traits.
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Evidence 1: Sara and her parents
2.​ Some New Jersey middle school students were interested in understanding how people
inherit their traits. To find out, they first randomly chose a person, Sara, in their class and
recorded her traits. Sara went home that night and recorded her parents’ traits and brought
her observations back to class the next day. Here are their results:
Sara
Dimples
Unattached Earlobes
Widow's Peak
Curved Thumb
Can Roll Tongue
Can’t Taste PTC
Sara's Father
Dimples
Unattached Earlobes
Widow's Peak
Straight Thumb
Can Roll Tongue
Can Taste PTC
Sara's Mother
Dimples
Unattached Earlobes
Straight Hairline
Curved Thumb
Can’t Roll Tongue
Can’t Taste PTC
3.​ In pairs talk about all the reasons why you are selecting each arrow.
Trait
Model A: Strong Parent
Model B: Sex Model
#1 Dimples
#2 Earlobes
#3 Hairline
#4 Thumbs
#5 Tongue Rolling
#6 Taste PTC
4.​ Can any models can be ruled out by the evidence? Explain why a piece of evidence
rules out a model.
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5.​ Here are ​two more models​ of how children inherit their traits from their parents. These
models were proposed by students in your class or other classes during the class discussion in
Lesson 1. In pairs, read each model. ​Circle which model is you think is better.
Model C: Strong Gene
Model D: Mixed Model
Some genes are stronger and some are
weaker. So kids get genes from their mom
and dad. Whichever version of the gene is
stronger wins for that trait. So you can get a
strong version of a gene for one trait from
mom and a strong version of a gene for a
different trait from dad.
Every child gets genes from mom and dad.
The genes all get mixed up together so that
if dad is tall and mom is short the kids will all
be medium. Since they mix there are no
genes that are stronger than any other
genes.
6.​ In pairs, read Evidence 2 (below) and discuss each piece of evidence. After discussing
the evidence, fill in the arrows diagram.
Evidence 2: Teresa and her parents
7. ​Sara, from Evidence 1, and Teresa are friends and they noticed that they have the same
traits. Students wondered if Teresa’s parents have the same traits as Sara’s parents (shown in
evidence 1). Here are their findings:
Teresa
Dimples
Unattached Earlobes
Widow's Peak
Curved Thumb
Can Roll Tongue
Can’t Taste PTC
Trait
Teresa's Father
No Dimples
Unattached Earlobes
Widow's Peak
Straight Thumb
Can Roll Tongue
Can Taste PTC
Teresa's Mother
Dimples
Unattached Earlobes
Straight Hairline
Curved Thumb
Can’t Roll Tongue
Can’t Taste PTC
Model C: Strong Gene Model
Model D: Mixed Model
#1 Dimples
#2 Earlobes
#3 Hairline
#4 Thumbs
#5 Tongue Rolling
#6 Taste PTC
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8.​ Can ​either model(s) can be ruled out​ by these pieces of evidence? Explain.
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Individually, answer this question.
9.​ What is the best model for how children inherit traits from their parents? Use details and
evidence to support your claim.
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