A pedigree chart is a diagrammatic representation showing the occurrence and appearance of phenotypes of a particular gene/traits and its ancestors from one generation to the next establishing relationships between individuals in a family.
Using the letter A for a dominant allele and a for a recessive allele, the genotype of individual I-1 is Aa.
In the key pedigree nomenclature, an individual marked with the black ink is affected with the trait (and this trait is dominant - A).
Looking at the F1 generation, there are males affected and females as well.
For inheritance of the trait, just one copy is enough to become affected.
Therefore, the male parent is heterozygous for the trait and the female normal (aa) to enable the production of both affected and non-affected individuals.
