Pedigree Analysis

Why do pedigree analysis? Problems with human genetics human generation span = 20-30 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 http://stingaling.files.wordpress.com/2010/08/cabbage-patch.jpg

Pedigree symbols

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

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

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

http://www.uic.edu/classes/bms/bms655/gfx/pedigree1.gif

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

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

http://www.uic.edu/classes/bms/bms655/gfx/pedigree5.gif

Some X-linked dominant diseases are lethal for males http://www.uic.edu/classes/bms/bms655/gfx/pedigree6.gif

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

http://www.uic.edu/classes/bms/bms655/gfx/pedigree8.gif

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