Biology 6

Pedigree Worksheet Name ____________________________________

I

1 2

II 1 2 4 5

3 6 7 8

III

1 2 3 4 5

1. Which members of the family above are afflicted with Huntington’s Disease? _________________________________

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? ____________________________

3. How many children did individuals I-1 and I-2 have? _______________________________________________

4. How many girls did II-1 and II-2 have? ______________ How many have Huntington’s Disease? ________________

5. How are individuals III-2 and II-4 related? ________________________ I-2 and III-5? _________________________

6. The pedigree to the right shows a family’s pedigree

for Hitchhiker’s Thumb. Is this trait

dominant or recessive? _______________________

7. How do you know? _________________________

___________________________________________

8. How are individuals III-1

and III-2 related? ________________________

9. How would you name the 2 individuals that

have hitchhiker’s thumb? ___________________

10. Name the 2 individuals that were

carriers of hitchhiker’s thumb. ______________

11. Is it possible for individual IV-2 to be a carrier? ___________ Why? ________________________________________

12. The pedigree to the right shows a family’s pedigree

for colorblindness. Which sex can be carriers of

colorblindness and not have it? ______________________

13. With this in mind, what kind of trait is

colorblindness (use your notes)? ______________________

14. Why does individual IV-7 have colorblindness?

_________________________________________________

15. Why do all the daughters in generation II carry the

colorblind gene? ____________________________________

16. Name 2 IV generation colorblind males. _________

= Huntington’s

Disease

I

II

III

IV

1 2

1 2 3 4

2 1

1 2 3

3 4

I

III

IV

II

1 2 3 4 5 6 7 8

**half-shaded = carrier of disease

Name ____________________________________

Genetics Pedigree Worksheet

A pedigree is a chart of a person’s ancestors that is used to analyze genetic inheritance of certain traits –

especially diseases. The symbols used for a pedigree are:

female, unaffected

female, affected

male, unaffected

male, affected

• Siblings are placed in birth order from left to right and are labeled with numbers.

• Each generation is labeled with a Roman numeral.

o Example: we would name an individual II-3 if he/she was in the second generation and the 3 rd

child born

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I

1 2 3 4 5 6

II

1 2 3 4 5 6 7 8 9

III

1 2 3 4 5 6 7 8

Try to identify the genotypes of the following individuals using the pedigree above.

(homozygous dominant, homozygous recessive, heterozygous)

• III-3: ___________________________________

• II-1: ____________________________________

• I-1: ____________________________________

• II-4: ____________________________________

1. Is this trait dominant or recessive? Explain your answer.

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

2. How can you know for sure that individuals II-3 and II-4 are heterozygous?

___________________________________________________________________________________________

___________________________________________________________________________________________

3. Brown eyes are a dominant eye-color allele and blue eyes are recessive. A brown-eyed woman whose father

had blue eyes and whose mother had brown eyes marries a brown-eyed man whose parents are also brown-

eyed. They have a son who is blue-eyed. Please draw a pedigree showing all four grandparents, the two

parents, and the son. Indicate which individuals you are certain of their genotype and where there are more

than one possibilities.