PEDIGREE CHARTS A family history of a genetic

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

What is a pedigree chart? ¢ Pedigree charts show a record of a specific disease or trait in a family. They can be used to study the spread of a hereditary condition They are particularly useful when there are large families and a good family record over several generations. l Cheap and non invasive way to investigate if a disease may be genetic l © 2007 Paul Billiet ODWS

Why is studying human genetics so hard? o o o Cannot breed humans by selection Long time frame for each generation Complexity of human genome Moral/Ethical barriers Relatively few offspring Complex lifespan/lifestyle/epigenetic factors © 2007 Paul Billiet ODWS

Symbols used in pedigree charts ¢ ¢ ¢ Normal male Affected male Normal female Affected female Marriage Half-filled box is a known carrier of the trait, but not expressed (seen). © 2007 Paul Billiet ODWS A marriage with five children, two daughters and three sons. The eldest son is affected by the condition. Eldest child Youngest child

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

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

Organising the pedigree chart ¢ ¢ Individuals in each generation are identified by numerals numbered from the left to right Therefore the affected individuals are II 3, IV 2 and IV 3 I II IV © 2007 Paul Billiet ODWS

Reading a Pedigree: Dominant inheritance ¢ Gen I : Dad has the trait, mom does not. l ¢ What are the possible genotypes for mom? Gen II : One daughter and son has the trait and one son does not.

A Royal Pedigree: Sex. Linked Inheritance ¢ ¢ ¢ Gen 1: Albert and Victoria are married and do not have hemophilia Gen 2: They have 6 children: 3 boys and 3 girls. Leopold is the only child who has hemophilia. How do you describe generation 3 and 4?

Draw our own Pedigree ¢ Widows Peak is a basic Mendelian dominant trait. A male with widows peak marries a woman who does not have widows Peak. l They have 3 children, 2 boys and 1 girl.

Draw our own Pedigree ¢ ¢ We know that Color Blindness follows a Sex-Linked Recessive Pattern Color blind dad marries a mother who can see color. l They have 3 children (2 boys, 1 color blind) and 1 color blind girl. What is the mothers genotype? l The color blind girl marries a man who can see color and they have 1 boy and 2 girls. Can their son see color? What are the possible genotypes for the girls?