Lisa learned that blue eye color is a recessive trait and brown eye color is a dominant trait. She became puzzled because she and her sister, Sara, both have blue eyes. Her parents, Joan and Greg, both have brown
eyes. Lisa wants to know how she and her sister could have blue eyes. As shown below, Lisa drew her family
tree showing eye colors (pedigree), beginning with both sets of grandparents,
Mary
Jake
Leslie
Paul
Blue-eyed male
Blue-eyed female
Brown-eyed female
Brown eyed male
Sue
Joan
Greg
Pete
Sara
Lisa
Why docs Lisa have blue eyes?
Their parents both have an allele for blue eyes, but it is not expressed.
G Blue eye color is a trait that is expressed in every other generation.
Eye color is not a hereditary trait, so Lisa and her sister did not inherit their eye color from their parents.
The grandparent's genes for eye color are not influencing Lisa and her sister's genes for eye color.