1. Human Pedigrees 12.3 pg 255

2. Pedigrees  Family tree that records and traces the occurance of a trait in a family.  Analyze patterns  Applies Mendel’s concepts of dominant and recessive alleles.  Shapes: Males- squares Females- circles

3. Pedigree traits  Individuals showing (expressing) the trait are shaded( colored in)  Recessive traits have “ee” genotypes  Pedigrees can be analyzed for recessive, dominant, and sex-linked disorders

4. Recessive Traits  Most human genetic disorders are in this group.  Range of severity.  Examples- Albinism- lack of pigment TaySachs- fatal nerve disease Cystic fibrosis- defective protein- thick mucous buildup affects breathing, digestion, liver. 1/25 people of European ancestry are affected in the U.S.

5. Carrier  Has one allele but does not show the symptoms.  Heterozygous for the trait.  Some pedigrees show such individuals as a half shaded circle.  If two carriers have a child there is a ¼ chance the child will have the disorder.

6. Dominant Traits  Only one allele needed to have disorder (heterozygous Aa or homozygous AA).  Less common  Disorder is in every generation  Examples- Polydactyl- extra fingers and toes Achondroplasia- dwarfism  All individuals are heterozygous.  Homozygous is fatal.

7. Dominant Traits continued  Note- Dominant alleles are not found more often in populations.  Most dominant disorders are fatal before reproductive age.  Exception-Huntington’s disease- nervous disorder- no symptoms until 30s or 40s- so trait passed on to children.

8. Sex-linked pedigrees  More men have the trait.  Review sex-linked notes

9. Genetic Counselor  Collects and analyzes family inheritance patterns  Helps interpret genetic test results.  PKU- phenyketonuria- tells if baby is missing and enzyme to process phenylalanine. Diet is critical.  Sweat chloride test- cystic fibrosis.  More than 250 different genetic tests available.  Confidentiality and bioethics an issue