When we are talking of dominance in genes, we have that a gene can present with certain variations, this variations are called alleles. Now acording to mendelian genetics in alleles we can have dominant alleles or recessive alleles.
When an allele is dominant it means thet every time this allele be present the trait thet code will show, it doesn't matter if the organism is homozygous (SS for example) or heterozygous (Ss for example) in both cases the person wil have smile dimples, now a recessive trait will only show itself when is in its homozygous form (ss) and in that case and only the person won't show smile dimples.
Slides suggestion
