Pedigree Charts
Unit 2- Genetics SBI 3U
• Pedigree charts are used to show records of families or individuals. • They are used because breeding humans is not possible. Shows ethical ways of studying human genetics. • Shows how possible conditions may be inherited. • Uses symbols to represent the individuals and their relationships to each other
What is a pedigree chart?
What symbols are used?
• Here we see a family with 5 children. • The pedigree chart shows that the second son is affected by the condition.
• Below is a pedigree of 4 generations – 20 people. • Generations are identified by Roman numerals. • Individuals in each generation are identified by Arabic numerals numbered from the left. Therefore the affected individuals are II3, IV2 and IV3.
Dizygotic twins
Adopted
Monozygotic twins
Sex unspecified Number of children of each sex indicated Affected
Consanguineo us marriage
Divorced Multiple marriage
Extra marital union
• The half filled circles and squares show the carriers of the disorder
• This shows that the disorder/condition is carried by the females but expressed in the males. • This is called a Sex – Linked condition.
• Now for the Spanish connection: Victoria’s youngest child, Beatrice, gave birth to one daughter, one normal son, and two hemophilic sons. Looking at the pedigree of the royal family, identify which of Beatrice’s children received the hemophilic gene; why can you make this conclusion? • Notice that Beatrice’s daughter, Eugenie, married King Alfonso XIII of Spain and had six children, one of whom was the father of Juan Carlos, the current King of Spain. Would you predict that Juan Carlos was normal, a carrier, or a hemophilic?
• Is the condition Sex linked or not?
• Study the following pedigree chart. How is this disorder inherited? Write in the genotypes for each individual.
Study the following pedigree chart. How is this disorder inherited? Write in the
genotypes for each individual.
Study the following pedigree chart. How is this disorder inherited? Write in the genotypes for each
individual
Is the trait dominant or recessive?
Is the trait dominant or recessive? Who are the possible carriers?