A family history of a genetic condition or trait PEDIGREE CHARTS A family history of a genetic condition or trait

What is a pedigree chart? Pedigree charts show a record of the family of an individual. They can be used to study a hereditary condition or trait. They are especially useful when there are large families that cover several generations. © 2007 Paul Billiet ODWS

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

ORGANIZING A PEDIGREE CHART Generations are identified by Roman numerals & are on different levels. I II III IV

Males are represented by the square Females are represented by the circle I II III IV

Parents are connected with a horizontal line. Offspring are below the parents and the bracket is connected by a vertical line. Siblings are within the same bracket.

READING THE SYMBOLS USED IN PEDIGREE CHARTS A marriage with five children, two daughters and three sons. The middle son is affected by the condition. Eldest child  Youngest child Normal male Affected male Normal female Affected female Marriage © 2007 Paul Billiet ODWS

Sex Linked Disorder: Color-Blindness

Hemophilia is a blood disorder that affects blood clotting Hemophilia is a blood disorder that affects blood clotting. It comes from a recessive gene on the x-chromosome. Use the pedigree chart on worksheet to trace hemophilia through the Royal family.

Closure: Explain how you can determine if a person is affected by a specific condition by looking at a pedigree chart. Explain what it means when a trait is “x-linked” Is it possible to be a carrier for a gene that codes for a disorder without showing any symptoms? How?