What are dominant and recessive alleles?
When a gene determines a trait, the pair of alleles we inherit for that gene will determine how the trait looks in us. Some alleles may have a stronger effect on the observed trait than others. Dominant alleles always determine the observable trait, but recessive alleles only determine the observable trait when two recessive alleles are paired with one another. For example, it is thought that a single gene determines the shape of your hairline with a dominant allele for the Widow’s Peak and a recessive allele for the straight hairline. This means that if you inherit just one allele for the dominant Widow’s Peak hairline, you will have a Widow’s Peak. The only way for you to have a straight hairline is if you receive the recessive straight hairline allele from both parents.
