PEDIGREE CHARTS © 2007 Paul Billiet ODWS

Pedigree

A family history of a genetic condition PEDIGREE CHARTS A family history of a genetic condition © 2007 Paul Billiet ODWS

What is a pedigree chart? Pedigree charts show a record of the family of an individual trait/disorder They can be used to study the transmission of a hereditary condition They are particularly useful when there are large families and a good family record over several generations. © 2007 Paul Billiet ODWS

Studying human genetics Pedigree charts offer an ethical way of studying human genetics Today genetic engineering has new tools to offer doctors studying genetic diseases A genetic counselor will still use pedigree charts to help determine the distribution of a disease in an affected family © 2007 Paul Billiet ODWS

Most common signs and symbols used in pedigree analysis

Symbols used in pedigree charts A marriage with five children, two daughters and three sons. The eldest son is affected by the condition. Eldest child  Youngest child Normal male Affected male Normal female Affected female Marriage © 2007 Paul Billiet ODWS

Organizing the pedigree chart A pedigree chart of a family showing 20 individuals © 2007 Paul Billiet ODWS

Organizing the pedigree chart Generations are identified by Roman numerals I II III IV © 2007 Paul Billiet ODWS

Organising the pedigree chart Individuals in each generation are identified by Arabic numerals (1, 2, 3, etc.) numbered from the left Therefore the affected individuals are II-3, IV-2 and IV-3 I II III IV © 2007 Paul Billiet ODWS

Attached Ear Lobes If the disease was an attached earlobe than that person would have recessive information with a genotype of “ee”. They would be shaded in. If they were not shaded in then they would have at least one E.

Organizing the pedigree chart Thus, using this same chart, the person II-3 would be “ee” since they are shaded in. The parents I-1, and I-2 must be Ee and Ee in order to have a child with both “ee”. I II III IV © 2007 Paul Billiet ODWS

Huntington’s Disease Neurodegenerative genetic disorder Mid-life onset (around 40-50) It is much more common in people of Western European descent than in those of Asian or African ancestry Can affect men and women Uncontrolled body movements Mental abilities generally decline into dementia. Life expectancy of about 20 years after diagnosis No cure, some treatment for symptoms

Dominant Trait Huntington Disease