1. Patterns in Pedigrees

2. Make observations based on the pedigree below:

3. What is a Pedigree you ask?
A pedigree is a diagram (or family tree) that shows family history
It follows one trait throughout the generations of a family
Scientists use pedigrees to help study how traits are inherited in humans
= Male
= Female

4. So What do the Patterns in Pedigrees tell us?
The patterns give us clues about how a trait is inherited
Scientists use the clues to figure out whether the trait is dominant or recessive

5. An Example
Explain how the pedigree tells you whether the orange allele is dominant or recessive.

6. Why is it Important to Know how Traits are Inherited?
Well, there are many diseases that can be passed down from parents to offspring
Depending whether the trait is dominant or recessive a pedigree is used to help parents figure out the chances of passing a disease onto their offspring

7. Details About Human Genetic Diseases…
A person can be a carrier
A carrier is someone that carries the recessive gene for a disease but DOES NOT have the disease
A carrier can pass the allele onto their offspring/children
Not all genetic disorders are recessive, some are dominant

8. Pedigree of PKU
Is this condition dominant or recessive?

9. Recessive Conditions in Pedigrees…
Recessive conditions may skip a generation
Like in the PKU pedigree
In order to inherit a recessive condition you must inherit two recessive genes

10. Pedigree of Polydactyl
Is this condition dominant or recessive?

11. Dominant Conditions in Pedigrees…
Dominant conditions DO NOT skip a generation
The condition appears in every generation of the family

12. Not All Traits are Either Dominant or Recessive…
There are two other types of inherited traits:
Co-Dominance:
Two traits appear at the same time if the organism is heterozygous
Incomplete Dominance:
Neither allele is dominant or recessive
Heterozygous organisms show a blend of each allele (ex. A red and white flowering plant make a pink plant)

13. Are there Human Traits that are Co-dominant?
Yes, blood type…there are 4 types: A, B, AB, and O
Look at the chart below
Use it to determine which blood types are co-dominant and which is Recessive.