An organism with one dominant and one recessive gene for a trait is called a heterozygote.

Here's a breakdown:

* Heterozygous: Means having two different alleles (versions) of a gene.

* Dominant: The allele that expresses itself even if only one copy is present.

* Recessive: The allele that only expresses itself if two copies are present.

For example, let's say a flower has a gene for color with two alleles:

* R: Red (dominant)

* r: White (recessive)

A heterozygous flower would have the genotype Rr. Even though it carries the recessive "r" allele, the dominant "R" allele will be expressed, and the flower will be red.