Passage I

The figure below is a pedigree that shows the inheritance of a trait, Trait G, in a family. The presence of Trait G in an individual is determined entirely by Gene G. Gene G has 2 alleles: G, which is dominant, and g, which is recessive.

Each individual represented in the pedigree was assigned a number (shown below the symbol for the individual) for reference. Scientists determined that the Gene G genotype of Individual 20 is gg and that the Gene G genotype of Individual 21 is Gg. Based on this information, the scientists concluded that Trait G is a recessive trait.