Download Worksheet for Pedigree Analysis and Practice Key and more Exercises Genetics in PDF only on Docsity!
Pedigree Analysis Name __________________________________
I
II 1 2 4 5
III
- How many children did individuals I-1 and I-2 have? ___ 6 ___ How many HAVE Huntington’s Disease? ___ 3 ___
- How many daughters did II-1 and II-2 have? ___ 2 _____ How many sons? _____ 1 _____
- How are individuals III-2 and II-4 related? ____Uncle/Niece______ I-2 and III-5? ___Grandmother/Grandson_____
- 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 trait? _____Dominant________
- Write the genotypes over all known individuals. Represent unknowns with question marks.
- The pedigree to the right shows a family’s pedigree
for Hitchhiker’s Thumb. Is this trait
dominant or recessive? __recessive___________
- How do you know? __If it was dominant, either
Parent III-1 or III-2 would have the trait _____
- Therefore, write the genotypes of above the
individuals with Hitchiker’s Thumbs (use T / t ).
- How are individuals III-1 and III-2 related?
__cousins AND married______________
- Write the genotypes above individuals
III-1 and III-2.
- Is it possible for individual IV-2 to be a carrier? yes Why or why not? __parents are heterozygous____________
- The pedigree to the right shows a family’s pedigree
for colorblindness. Which sex can be carriers of
colorblindness and not have it? ______females___________
- With this in mind, what kind of trait is
colorblindness (use your notes)? Sex linked and recessive
- Write the genotypes above all individuals.
- Why do all daughters in generation II carry the
colorblind gene? they received a colorblind allele from dad__
- If individual IV-7 had children, what percentage
of her sons would you expect to be colorblind? _100%_____
= Huntington’s
Disease
I
II
III
IV
1 2
1 2
3 4
1 2
1 2 3
3 4
I
III
IV
II
1 2 3
4 5 6 7 8
half-shaded = carrier
Hh hh
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T? T?
T? T?
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Tt T?
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Pedigree Practice
On a separate sheet of paper, draw the pedigrees using the given information
and then answer the questions that follow.
- In the world of Harry Potter, having magical abilities is a completely recessive trait (muggles are individuals
which express the dominant non-magical trait). Draw a pedigree that traces magical abilities through three generations of
Harry Potter’s family. Harry is a wizard. His father James was a wizard and his mother Lily was a witch. Both of James’s
parents had magical abilities; however, Lily’s parents and her sister Petunia were all muggles. Harry’s Aunt Petunia married
Vernon Dursley and had a son, Dudley. The Dursleys are all non-magical muggles (and proud of it!). Shade the
circles/squares of all magical individuals. Write the names of each individual as well as their genotypes underneath each
circle/square. If an allele is unknown, use a question mark.
a) Would it have been possible for Vernon and Petunia Dursley to have a magical child? Why or why not?
It would be possible if both Vernon and Petunia are heterozygous, but it is unknown whether they are
homozygous or heterozygous.
`
b) Harry married Ginny Weasley. What would be the expected genotypes and phenotypes of their children?
Both Ginny and Harry are magical, which is a recessive trait. This means ALL of their children would have
the magical recessive trait.
mm
Lily
mm
James
mm
Harry
mm
Ginny
mm
mm
Mm Mm
Petunia
M?
Dudley
M?
Vernon
M?
- Achondroplasia is a common form of hereditary dwarfism that causes very short limbs, stubby hands and an
enlarged forehead. Draw the pedigree that traces this disorder in the Roloff family. Matt and Amy Roloff both have
achondroplasia dwarfism. Of their four children, three are of normal height (Jacob, Molly and Jeremy) and one has
achondroplasia (Zachary). Shade the circles/squares of the individuals with dwarfism.
a) Achondroplasia is an example of which type of inherited trait? How do you know?
Dominant. If it was a recessive trait, all of Matt and Amy ’ s children would have achondroplasia.
b) Both Matt’s parents and Amy’s parents are of average height. What does this mean about how they must have
inherited dwarfism?
It must have been a mutation.
- Hemophilia is a recessive, sex-linked disorder which causes an inability to clot when bleeding. Ray and Elaine
Smith were married in 1970. Neither Ray nor Elaine had hemophilia. They had two daughters and then a son. Both
daughters, Alicia and Candace, had normal clotting abilities and never had any children of their own. The son, Mike, had
hemophilia and married Beth, who did not. They had two children of their own, first Gregory and then Victoria.
Surprisingly, Victoria had hemophilia but Gregory did not. Draw the pedigree that traces hemophilia in the Smith family,
shade in the circles/squares of the individuals with the blood disorder.
a.) Why is it surprising that Victoria had hemophilia but Gregory did not?
Because it is more common for males to have sex linked disorders than female. Victoria had to receive
two recessive alleles in order to have hemophilia. Gregory would have had to have only received one in
order to have the disorder.
b.) If Victoria has children, what do you automatically know about her…
Daughters?
They will at least be carriers of hemophilia.
Sons?
All of her sons will have hemophilia.
Elaine
X
N
X
n
Roy
X
N
Y
Beth
X
N
X
Alicia n
X
N
X
?
Candace
X
N
X
?
Mike
X
n
Y
Gregory
X
N
Y
Victoria
X
n
X
n
