Am I Getting Dumber

Am I Getting Dumber

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Am I Getting Dumber

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Name ________________________

Period _______________________

Pedigree Activity

“Am I Getting Dumber?”

Reflections by Lisa Simpson

July 22, 2015

Dear Diary,

My recent engagement to Milhouse has gotten me both excited and worried. I’m

spending a lot of time making wedding arrangements and I’m finding that I am forgetting

a lot of important details.

At first I thought it was just all of the stress involved with

getting married.

But then I learned about a rare trait that runs through my family called

the “Homer” trait. Individuals that have this trait gradually get dumber throughout their

lives.

It appears at different times of life in different family members.

Could it be that I

actually have this trait?

Am I getting dumber?

Help!

Here’s what I know:

1.

The “Homer” trait is sex-linked and recessive.

2.

My dad, Homer, and brother, Bart, both express the “Homer” trait. My mother,

Marge, does not express the “Homer” trait.

I’m not sure about my sister Maggie.

3.

My Grandpa on my father’s side, Grampa, expresses the “Homer” trait. My

grandmother on my father’s side, Mona, does not.

4.

Neither grandparent on my mother’s side, Mr. and Mrs. Bouvier, express the

“Homer” trait. I do know, however that Mrs. Bouvier was a carrier of the trait.

Neither of my mom’s sisters, Patty and Selma, express the “Homer” trait.

Here’s what I need you to do:

1.

Construct a pedigree illustrating the inheritance of the “Homer” trait through

my family.

The following individuals should be included in the pedigree:

Homer, Marge, Bart, Lisa, and Maggie Simpson

Grampa and Mona Simpson

Mr. Bouvier, Mrs. Bouvier, Patty, and Selma

2.

In your pedigree, use a solid shape

to indicate affected individuals and

a half solid shape

to indicate heterozygotes (also called carriers).

Put a

?

in the shape to indicate unknown phenotypes.

3.

In the table on the next page, indicate the genotypes and phenotypes of each

individual.

Assume X

H

= “Homer” and X

+

= Normal.

Remember that males

only carry one X chromosome! For example, a male with the “Homer” trait

would have the genotype X

H

Y.

A female carrier would have the genotype

X

+

X

H

.

For unknown genotypes, write down all possible options.

Name ________________________

Period _______________________

In you lab notebook, do the following:

1)

Construct a pedigree

2)

Copy this table into your lab notebook and fill it in with as much information

as you can.

Name

Genotype

Phenotype

Homer

Marge

Bart

Lisa

Maggie

Grampa

Mona

Mr. Bouvier

Mrs. Bouvier

Patty

Selma

3) Read the next passage in Lisa’s diary, shown below, then respond as indicated.

March 3, 2026

Dear Diary,

I am now 34 years old and have not yet gotten dumber.

I therefore do not

express the “Homer” trait. I am relieved by that, but now have a new

worry.

Milhouse and I have had four children in the past 11 years: two

boys, named Vincent and Albert, and two girls, named Ophelia and

Scarlett. Even though Milhouse does not express the “Homer” trait I am

worried that some of my children might have it.

Help!

Determine the probability that each of their four children express the “Homer”

trait, then find the probability that each of the daughters is a carrier for the

“Homer” trait? Show ALL your work, including Punnett squares and genotypes.