Analyzing Human Pedigrees - Autosomal Dominant
When completing this pedigree with autosomal dominant inheritance, individuals that are non-shaded are expressing the recessive phenotype and have a genotype of “dd”. Shaded individuals will either have a genotype of Dd or DD, or D_ (not enough information to determine).
- Traits do not skip generations (generally). If the trait is displayed in offspring, at least one parent must show the trait.
- If parents don't have the trait, their children will not have the trait.
- In some cases, having two copies of the allele (DD) may result in a more severe form of the condition
- In other cases, two copies of the allele is a fatal condition (dwarfism). In which case, all individuals with the condition are Dd.
Pedigree Analysis
1. In humans, polydactyly is a condition where a person has extra fingers or toes. The allele that causes this trait is dominant. A person with Dd or DD will have extra digits. Fill out the pedigree of this family where polydactyly has been observed.
2. Marfan syndrome affects the body's connective tissue. Individuals may be very tall and have long limbs and fingers. Some speculate that Abraham Lincoln may have had Marfan syndrome.
Other Resources
Human Genetic Disorders - Pedigree Charts