What is the effect of a dominant allele in a heterozygous genotype?

In a heterozygous genotype, where one allele is dominant and the other is recessive, the dominant allele expresses its trait and effectively masks the effect of the recessive allele. This means that even though both alleles are present, the phenotype – or the observable traits – of the individual will reflect the characteristics associated with the dominant allele.

For example, if we consider a gene that determines flower color where purple is a dominant trait (represented as "P") and white is a recessive trait (represented as "p"), a plant with a heterozygous genotype (Pp) will display purple flowers. The presence of the dominant allele (P) overrides the recessive allele (p), thus showcasing the dominance in genetic expression.

This phenomenon of dominance is fundamental in understanding inheritance patterns in organisms and highlights how dominant traits can be passed on to the next generation regardless of the presence of a recessive counterpart.