Final answer:
A person with two different alleles for a gene is heterozygous, and will express the dominant trait phenotype.
Step-by-step explanation:
When a person has two different alleles for a particular gene, he or she is said to be heterozygous for those alleles. In genetics, having two identical alleles for a gene is referred to as homozygous, which can either be homozygous dominant (e.g., AA) or homozygous recessive (e.g., aa). On the other hand, an individual carrying one dominant and one recessive allele (e.g., Aa) is considered heterozygous. This means that the phenotype of the dominant trait will be expressed, overpowering the recessive allele's potential effect.