Post on 27-Mar-2015
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.