Pedigree charts are used to determine the inheritance of traits by analyzing family medical histories and records since experimental crosses cannot be done with humans. The charts use symbols to represent individuals and their traits, generations, and relationships. By completing a pedigree chart, genetic diseases can be traced to where they came from in a family tree to help determine if a trait is inherited autosomal recessively, dominantly, X-linked, or Y-linked.

1. Pedigree charts

3. Pedigree charts Some symbols to remember: Normal female Normal male Normal (sex is unknown) Female with phenotype of interest Male with phenotype of interest Person with phenotype of interest (unknown sex) Female heterozygous for recessive allele Male heterozygous for recessive allele

4. Pedigree charts Some symbols to remember: I II First born Last born Roman numerals represent generation siblings

5. Pedigree charts Some symbols to remember: I II One-egg Monozygotic Identical twins Two-egg dizygotic fraternal twins

6. Pedigree charts How do we use a pedigree chart? When people have children… I II III If this child had a genetic disease, we can trace who it came from by completing the pedigree from family and medical records Mother’s family Father’s family

7. Pedigree charts Hemophilia in the royal family I II III IV0

8. Pedigree charts Hemophilia

9. Pedigree charts Hemophilia in the royal family

10. Pedigree charts Royal Family Historical Record

11. Pedigree charts Albino

12. Pedigree charts Pedigree showing albinism

13. Pedigree charts Tay Sachs

14. Pedigree charts Pedigree showing Tay Sachs

15. Pedigree charts Autosomal recessive: Involves a recessive allele on a non-sex chromosome Autosomal dominant: Involves a dominant allele on a non-sex chromosome X-linked recessive: Involves a recessive allele on the X-chromosome X-linked dominant: Involves a dominant allele on the X-chromosome Y-linked: Involves an allele on the Y-chromosome