Eastern Regional High School
Honors Biology
Name:______________________
Mod:________ Date:__________
Unit 13 – Non-Mendelian Genetics
Worksheet - Pedigree Practice Problems
1. Identify the genotypes of all the individuals in this pedigree. Assume that the trait is an autosomal
recessive disorder.
1
1
1
1
3
2
2
2
2
3
4
4
5
6
3
5
7
8
9
4
5
1
6
2
a. How many generations are presented in this pedigree? ______________
b. We know that the trait is a recessive disorder. What clues are provided in the pedigree that would
allow you to confirm this conclusion?
_____________________________________________________________________________
_____________________________________________________________________________
c. Shade in half of the circle (or square) for all the individuals that are hybrid in the pedigree.
d. What is the genotype of the 6th individual in the fourth generation? ___________________
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e. Explain why some individuals can have multiple genotypes. Provide an example.
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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2. Examine the pedigree below for an autosomal recessive disorder. Determine the genotypes of all
the individuals in the pedigree.
1
1
1
2
2
3
2
3
3
4
4
5
4
5
6
7
6
a. What is the genotype of individual 2 in the first generation in the pedigree? Explain your answer.
_____________________________________________________________________
_____________________________________________________________________
b. What are the genotypes and phenotypes of individuals 3 and 4 in the second generation?
_____________________________________________________________________
c. Shade in the left half of the circle (or square) for all the individuals that are hybrid in the pedigree.
d. If the 4th individual in the 3rd generation married a female that was hybrid for the disease above,
what percentage of their offspring would exhibit the disease?
_____________________________________________________________________
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3. Examine the pedigree below for an autosomal dominant disorder. Determine the genotypes of all the
individuals in the pedigree.
1
1
1
1
2
2
2
3
4
3
2
5
4
3
6
5
7
6
4
a. What is the genotype of individual 1 in the first generation in the pedigree? Explain your answer.
_____________________________________________________________________
_____________________________________________________________________
b. What are the genotypes and phenotypes of individuals 4 and 5 in the second generation?
_____________________________________________________________________
c. If the 3rd individual in the 4th generation married a female that was homozygous recessive for the
disease above, what percentage of their offspring would exhibit the disease?
_____________________________________________________________________
d. We know that the trait is a dominant disorder. What clues are provided in the pedigree that would
allow you to confirm this conclusion?
4
_____________________________________________________________________
_____________________________________________________________________
e. Why are there no half-shaded individuals in this pedigree?
_____________________________________________________________________
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4. This pedigree shows the inhertiance of Huntington’s disease. There are no carriers for Huntington’s Disease- you
either have it or you don’t. With this in mind, is Huntington’s disease caused by a dominant or recessive allele?
___________________
I
II
1
2
1
2
4
5
3
6
7
8
III
1
2
3
4
5
a) Which members of the family above are afflicted with Huntington’s Disease? ____________________________
b) How many children did individuals I-1 and I-2 have? _______________________________________________
c) How many girls did II-1 and II-2 have? ___________ How many have Huntington’s Disease? _______________
d) How is individual III-2 and II-4 related? _____________________ I-2 and III-5? _______________________
5. The pedigree to the right shows the passing on
of Hitchhiker’s Thumb in a family. Is this trait
dominant or recessive? ____________________
How do you know? ______________________
I
a) How are individuals III-1
and III-2 related? ________________________
b) Name 2 individuals that
have hitchhiker’s thumb. __________________
c) Name 2 individuals that are
carriers of hitchhiker’s thumb. ______________
1
2
1
2
II
II
I
3
1
2
IV
1
6
4
2
3
3
4
6. The pedigree to the right shows the passing on of colorblindeness.
What sex is the only one that can be carriers of
colorblindness? __________________________
I
a. Is it possible for individual IV-2 to be a carrier?
__________
Why? __________________________________
b. With this in mind, what kind of non-mendelian
trait is colorblindness? ______________________
c. Why does individual IV-7 have colorblindness?
__________________________________________
d. Why do all the daughters in generation II carry
the colorblind gene? _________________________
II
II
I
IV
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e. Name 2 IV generation colorblind males. _________
7
2
3
4
5
6
7
Alkaptonuria is an inherited defect characterized by darkening cartilage in the ears, melanin spots in the
eyes, proneness to arthritis, and darkening of urine upon exposure to air. It is caused by a metabolic error
that results in the failure to produce an enzyme called homogentisic acid oxidase (HGAO). Because normal
amounts of the HGAO enzyme are missing, homogentisic acid (HGA) is not used and builds up in the body.
Use this pedigree for Alkaptonuria to determine the genetic basis of this trait. Determine the
genotypes of all the individuals in the pedigree above.
1
1
1
2
2
3
4
5
6
3
4
1
2
4
3
2
7
5
8
6
9
7
8
4
3
a. Based on the info in the pedigree is this trait autosomal or sex-linked? _________________
b. Is this trait produced by a dominant or recessive allele? _____________________
c. What is the genotype of the 3rd and 4th individuals in the third generation? ___________________
d. What is the genotype and phenotype of 4th individual in the fourth generation?
__________________________________________
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