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 CHARTGenerations 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

Normal male

Affected male

Normal female

Affected female

Marriage

A marriage with five children, two daughters and three sons. The eldest son is affected by the condition.

Eldest child Youngest child

© 2007 Paul Billiet ODWS

SEX LINKED DISORDER: COLOR-BLINDNESS

Genetic Counselors use a pedigree chart to predict the probability of transmitting an inherited disorder.

Cystic Fibrosis – autosomal recessive

Huntington’s Disease is autosomal dominant.

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.