1. 3.4 Review PBS

2. How are pedigrees used to track diseases?
We label the individuals as affected, carriers (if the trait is recessive), or unaffected by coloring.
Characteristics of a dominant pedigree are:
Every affected individual has at least one affected parent
Affected individuals who mate with unaffected individuals have a 50% chance of transmitting the trait to each child
Two affected individuals may have unaffected children

3. How are pedigrees used to track diseases?
Characteristics of recessive pedigrees are:
An individual who is affected may have parents who are not affected
All children of two affected individuals are affected

4. This happens if the trait is recessive
Why does sickle cell disease run in families, yet is not present in every generation?
This happens if the trait is recessive
In the pedigree below the two people in the first generation would be carriers.
Carriers have the recessive allele, but do not have the trait because of the dominant allele.
Both parents can pass on the recessive allele to their child and they can have the trait.

5. How can doctors and genetic counselors calculate the probability of a child inheriting a disease?
They can use punnett squares
25% of having the recessive trait
50% of being a carrier
50% of having the recessive trait
50% of being a carrier