1. Pedigree Analysis

2. Why do pedigree analysis?
Problems with human genetics
human generation span = years
parents produce fewer offspring
breeding experiments are unacceptable
Solution
analyze results of matings that have already occurred
collect history for a trait and assemble information into a family tree  pedigree
can help in predicting the traits of future offspring

3. Pedigree symbols

4. Pedigree of a family afflicted with neurofibromatosis,
an autosomal dominant genetic disorder

5. Inheritance patterns in pedigrees
autosomal dominant
autosomal recessive
x-linked dominant
x-linked recessive
y-linked

6. Autosomal dominant inheritance pattern
Due to a dominant gene on an autosome
males and females are equally affected
every affected individual has at least one affected parent
two affected individuals may have unaffected children
phenotype generally appears every generation
Characteristics
achrondoplasia, Huntington’s disease, widow’s peak, dimples, free lobes, tongue-rolling, brachydactyly, hypercholesterolemia
Examples

8. Autosomal recessive inheritance pattern
Due to a recessive gene on an autosome
males and females are equally affected
affected individual may have unaffected parents
all children of two affected individuals are affected
phenotype may skip a generation
Characteristics
cystic fibrosis, phenylketonuria, galactosemia, albinism, hemophilia, sickle-cell anemia, Tay-Sachs disease
Examples
Autosomal recessive inheritance pattern

10. x-linked dominant inheritance pattern
Due to a dominant allele on the x-chromosome
trait is never passed from father to son
all daughters of an affected male and a normal female are affected
all sons of an affected male and a normal female are normal
females are more likely to be affected than males
Characteristics
hypophosphatemia, Aicardi syndrome, fragile X syndrome
Examples

12. Some X-linked dominant diseases are lethal for males

13. x-linked recessive inheritance pattern
Due to a recessive allele on the x-chromosome
trait is never passed from father to son
Males more likely to be affected than females.
trait or disease typically passed from an affected grandfather, through carrier daughters, to half of his grandsons
Characteristics
red and green colorblindness, hemophilia, Duchenne muscular dystrophy, Hunter syndrome
Examples
x-linked recessive inheritance pattern

15. y-linked inheritance pattern
Due to an allele on the y-chromosome
when a male is affected, all of his male children are affected
Characteristics
male infertility and hypertrichosis pinnae
Examples
y-linked inheritance pattern