Whch word refers to groups of genes responsible for expressing a single trait?

The answer is alleles. This is the different forms of a gene that gives variation to a single trait phenotype to individuals in a population. Genes of an allele can either be dominant or recessive and their interaction is significant in organisms with multiple alleles.

Genotype

Explanation:

Genotype is defined as the genetic makeup of an individual, that is, the set of genes of that organism. The gene, in turn, can be defined as a specific nucleotide sequence of DNA that stores hereditary information. They present information that will be responsible for a given characteristic.

Each individual has a specific genotype that is made up of genes from their parents that will be kept for the life of the organism. This information is important to differentiate genotype from phenotype, because, while the genotype is not changed, the phenotype may undergo several modifications during the development of the organism.

the answer is sex-linked recessive.