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Pedigree Worksheet
I
1
II
1
2
2
4
= Huntington’s
Disease
5
3
6
7
8
III
1
2
3
4
5
1. Which members of the family above are afflicted with Huntington’s Disease?
I-1, II-2, II-3, II-7, III-3
2. 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
3. How many children did individuals I-1 and I-2 have? 6
4. How many girls did II-1 and II-2 have?
5. How is individual III-2 and II-4 related?
How many have Huntington’s Disease?
2
Uncle/Niece
6. The pedigree to the right shows the passing on
of Hitchhiker’s Thumb in a family. Is this trait
dominant or recessive? recessive
I
7. How do you know? III-1 and III-2 must have the
gene in order to have affected children, but do
not show the trait.
8. How are individuals III-1
and III-2 related? First Cousins
II
I-2 and III-5?
1
Grandmother/grandson
1
2
1
2
3
4
1
III
2
3
4
IV
9. Name 2 individuals that
have hitchhiker’s thumb. IV-1, IV-3
1
2
3
10. Name 2 individuals that were
carriers of hitchhiker’s thumb. III-1, III-2
11. Is it possible for individual IV-2 to be a carrier?
to be Hh also (punnett square)
Yes
Why? Since her parents were Hh, she has a 50% chance
12. The pedigree to the right shows the passing on of
colorblindness. What sex can ONLY be carriers of
colorblindness?
Female
I
13. With this in mind, what kind of non-mendelian
trait is colorblindness? Sex-linked
II
14. Why does individual IV-7 have colorblindness?
The individual received an affected X chromosome
from mother and father.
III
15. Why do all the daughters in generation II carry
the colorblind gene? Dad’s X chromosome has the
affected gene. Since daughter received an
X chromosome from the mother and the father,
one of their X chromosomes is also affected.
16. Name 2 IV generation colorblind males.
IV-1, IV-5
IV
1
2
3
4
5
6
7