If an organism has two different alleles for a trait, it is said to be what?

When an organism possesses two different alleles for a particular trait, it is characterized as heterozygous. This term originates from the Greek roots where "hetero-" means different, and "-zygous" pertains to the zygote that is formed during fertilization. In the case of heterozygosity, one allele may be inherited from one parent and a different allele from the other parent, which contributes to genetic diversity and may influence the organism's phenotype.

Heterozygosity is important in genetics as it can lead to variations in traits, especially when one allele is dominant over the other. This means that the dominant allele may mask the expression of the recessive allele in the organism's phenotype. Understanding heterozygosity is fundamental in genetics as it lays the groundwork for concepts such as inheritance patterns, genetic variation, and the potential for evolution within populations.