Download INTERPRETING A PEDIGREE

INTERPRETING A PEDIGREE
Name:
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Date:
Study the following figures to learn how family members are represented in a
pedigree.
Use the pedigree of the Lee family to answer the questions that follow.
The circle represents a female.
The square represents a male.
Shaded shapes represent family
members with one expression of a
trait (for example, dimples).
Shapes that are not shaded
represent members with no
dimples. In this example, the
female has dimples.
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A horizontal line is used to connect
two parents.
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Lines connect parents and
children.
The oldest children are placed on
the left and the youngest on the
right. In this example, there are
three children — two females
and a male. The male child has
no dimples.
Observations
1. How many generations of the family are shown? ________________________________________
2. What do the squares represent?______________________________________________________
3. How many children did Mr. and Mrs. Lee have? ________________________________________
4. How many children were females? ___________________________________________________
5. Was the oldest child a girl or a boy? __________________________________________________
6. What is the ratio of dimples to no dimples among the grandchildren? _______________________
7. What do you think is the dominant trait — dimples or no dimples? Why? ____________________
What Did You Find Out?
1. Write a concluding statement about the chances of inheriting dimples in the Lee
family.
2. Why should you include as many generations as possible when you make a pedigree?
3. (a) Assume that Mrs. Lee has Dd genotype. What genotype must Mr. Lee have?
(b) Make a Punnett square to show the possible combinations of traits in the children.
(c) Does the pedigree agree with what you found? On the back of this page, explain
why or why not.
Study the pedigree and solve the puzzle of the missing genotypes.
 Use the following information to help you.
– A circle represents a female.
– A square represents a male.
– Shaded shapes represent individuals with freckles. Individuals who have freckles
have at least one dominant gene for freckles (FF or Ff).
– Shapes that are not shaded represent individuals with no freckles. They have two
recessive genes (ff).
 Fill in the blanks with the genotype for each individual. An example is done for you.
– Start by identifying the genotypes of individuals that you know for certain.
– For the second generation, draw Punnett squares to help you determine the unknown
genotypes. Hint: What combinations of genotypes produce the offspring in the third
generation?
 Answer the questions that follow.
What Did You Find Out?
1. How many grandchildren have:
(a) at least one dominant gene for freckles?
(b) two dominant genes for freckles?
(c) two recessive genes for freckles?
2. Write a concluding statement about the chances of inheriting freckles in this family.