Observations and results
Could you see how some traits were passed down? Did it look like having detached earlobes, a widow's peak, mid-digit hair and a straight thumb were all dominant traits?
Although the presence or absence of attached earlobes, a widow's peak, mid-digit hair and a hitchhiker's thumb are thought to be primarily genetically inherited traits, there is some controversy over exactly how they are inherited—in other words, they may be affected by more than one gene, more than two alleles or factors other than genetics. That said, having detached earlobes, a widow's peak, mid-digit hair and a straight thumb are generally considered to be dominant traits, although clearly their inheritance is complex. A dominant trait is one that only needs one copy of the dominant allele to be displayed. For a person to show a recessive trait, they generally need two alleles for the recessive trait. Because a person only needs one copy of the dominant allele to show the trait, they could be homozygous or heterozygous for the allele. This means that a person who shows a dominant trait could have a child with a person who shows the recessive trait (or even another person who shows the dominant trait) and the child may show either trait (because the parent with the dominant trait may be heterozygous). Two people who both show a recessive trait are most likely to have a child that also shows the recessive trait, but inheritance is often affected by other factors.
More to explore
The Royal Family: Physical Traits , from The House of Windsor
Your Family Health History , from the National Human Genome Research Institute
Dominant versus Recessive , from The Tech Museum of Innovation, Stanford at The Tech
Pedigree Analysis: A Family Tree of Traits , from Science Buddies
This activity brought to you in partnership with Science Buddies