Final answer:
When a person is a carrier for a trait but does not have the trait themselves, the condition of the alleles can be described as heterozygous.
Step-by-step explanation:
When a person is a carrier for a trait but does not have the trait themselves, the condition of the alleles can be described as heterozygous. In genetics, an individual has two alleles for each gene, and if they have different alleles, they are said to be heterozygous for that gene. In the case of being a carrier, the individual has one dominant allele and one recessive allele.
For example, let's consider the sickle cell anemia trait. It is caused by a mutant recessive allele. Individuals who inherit one copy of the mutant allele and one copy of the normal allele are carriers. They do not have the disorder themselves, but they can pass the mutant allele on to their offspring.
Overall, being a carrier means having a heterozygous genotype where one allele is dominant and the other is recessive.