how is a recessive allele different from a dominant allele

Answer 1

A dominant allele is an allele that will express the dominant phenotype when only one allele is present. In contrast, a recessive allele is an allele that is only expressed when both alleles are in the genotype.

For example, let's say you are examining the trait for rolling your tongue. Let's call the dominant allele, R, and the recessive allele, r. For the trait to be expressed, which means you have the ability to roll your tongue(have the dominant phenotype,) you would either have to have the genotype RR or Rr. Only if you have the recessive allele rr will you not be able to use your tongue, (the recessive phenotype).

Note: This example is only for educational purposes and to prove a concept.