Pedigree Worksheet Biology Worksheet Template (Page 2 of 2) in pdf

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

male, unaffected

female, affected

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

child born

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

III

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

(homozygous dominant, homozygous recessive, heterozygous)

• III-3: ___________________________________

• I-1: ____________________________________

• II-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.

Pedigree Worksheet Biology Worksheet Template Page 2

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