1. Pedigrees and Inheritance Patterns

2. Pedigrees Pedigrees show relationships within a family.
Pedigree charts contain the following information:
Square shaped symbol = male
Circle shaped symbol = female
Solid symbol indicates a characteristic or trait
a “carrier” can be shown using a half-filled shape.
Horizontal lines indicate marriages.
Vertical lines indicate children (oldest on the left).

3. Pedigree Charts Pedigree charts can be used to determine
Genotypes and phenotypes of family members.
Whether an allele is dominant or recessive.
The probability of a child inheriting an allele or trait.
The probability of a child inheriting a genetic disorder.

4. Albinism in Possums
Albinism in possums is caused by a mutation which results in no colour being produced.
Albino possums are therefore white.
The following is a pedigree chart showing the inheritance of albinism in a family of possums.

5. Albinism in Possums Key: female male Normal Albino 1 2 3 4 5 6 7 8 910 11 12 13 14 15 16

6. Albinism in Possums
Which characteristic, normal or albino colouring, is recessive?
Explain the reason for your answer
Using ‘Q’ to represent the dominant allele, and ‘q’ to represent the recessive allele, give the probable genotype of possum number 1.

7. Pedigree Problem
The pedigree chart following shows the inheritance of a genetic disease in humans.
The yellow boxes show individuals who have the disease.
Use the information on the chart to answer the question.

8. Pedigree Problem
Key:
Male
female
has disease: shaded
Is the allele for this disease dominant or recessive? Explain your answer