A heterozygous individual is often represented as Aa, where A represents the dominant allele and a represents the recessive allele. For example, if a gene controls the color of a flower, the dominant allele may code for red flowers (R) and the recessive allele may code for white flowers (r). A heterozygous individual (Rr) would have one allele for red flowers and one allele for white flowers. This individual would have red flowers because the dominant red allele is expressed, while the recessive white allele is not.
Heterozygosity is important because it increases genetic diversity within a population. It allows for a wider range of traits and adaptations, which can be advantageous in changing environments. Additionally, heterozygosity can help to mask the effects of harmful recessive alleles, reducing the risk of genetic diseases.