What describes the entire set of HLA antigens located on one chromosome?

The entire set of HLA antigens located on one chromosome is best described as a haplotype. Haplotype refers to a combination of alleles or a group of genes that are inherited together from a single parent. In the context of human leukocyte antigen (HLA) typing, each person inherits one set of HLA genes from their mother and one set from their father, resulting in two haplotypes that can be expressed.

Understanding the concept of a haplotype is essential in immunology and transplantation, as it plays a critical role in tissue compatibility and organ transplant success. Matching haplotypes between donors and recipients can help reduce the risk of transplant rejection due to immune responses against non-self antigens.

In contrast, the other terms have different meanings. An allele represents a specific variant of a gene at a particular locus, a trait is a characteristic or feature that can be physical or biochemical, and a phenotype refers to the observable characteristics of an organism resulting from the interaction of its genotype with the environment.