Pedigree Practice Problems questions worksheet PDF

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Name__________________________________ Date: __________________ Biology I

Pedigree Worksheet A family tree of sorts is called a pedigree. The symbols used for a pedigree are: female, unaffected

Siblings are placed in birth order from left to right and are labeled with Arabic numerals. Each generation is labeled with a Roman numeral. Therefore, the male exhibiting the trait in the pedigree below in the bottom, center would be identified as III-4.

female, affected male, unaffected male, affected

1 I 1

II

1

2

= Huntington’s Disease

2

4

5

3

6

7

8

III 1

2

3

4

5

1. Which members of the family above are afflected by Huntington’s Disease? i- 1 ii- 2, 3, 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? it is a dominant trait 3. How many children did individuals I-1 and I-2 have? 6

4. How many girls did II-1 and II-2 have? 2

5. How are individuals III-2 and II-4 related? ii- 4 is iii- 2 uncle

2

I

II

III

IV

12. The pedigree above shows the passing on of colorblindness. What sex is MOST likely to be carriers of colorblindness? females

13. Why does individual IV-7 (a female) have colorblindness? because the mum is a carrier and the dad has the diease

14. Why do all the daughters in generation II carry the colorblind gene? they must have the effected x chromosome which they receive from the father.

15. List 2 IV generation colorblind males. iv- 1 and iv- 5

3

16. Is this trait dominant or recessive? Explain your answer. recessive as only 3 people have the disease

17. What gave you the essential information to decide that II-3 and II-4 were heterozygous? as the trait is recessive, a person must receive both affected chromosomes to receive the trait, therefore causing a heterozygous pair

18. 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. Draw a pedigree (info above) showing all four grandparents, the two parents, and the son. Indicate each individuals possible genotypes....