How do scientists describe a genotype that has one copy of the recessive allele?

Heterozygous

Explanation:

A genotype describes which alleles of a particular gene a person has. We have two copies (alleles) of each gene, one from mom and one from dad, but these alleles can be different.

Often, these alleles can be dominant and recessive with regards to eachother. The dominant allele will always be displayed in the phenotype, whereas the recessive will not be presented, as it is masked by the dominant gene. If you have two copies of the dominant gene (homozygous) you will display the phenotype associated with the dominant genotype. If you have two copies of the recessive gene (homozygous) you will display the phenotype of the recessive gene.

If you have one copy of each (heterozygous), you will display the phenotype of the dominant gene, even though your genotype has a copy of each.