dominant vs. recessive phenotype

Dominant traits are manifested when only a single allele and it is capable of overriding another allele for a different trait. For example, allele B produces brown eyes while allele b produces blue eyes. Only one  B allele is needed for the child to inherit brown eyes while it takes two bb alleles for a child to inherit blue eyes. Attached earlobes are recessive while unattached earlobes are dominant.