1. (in genetics)

1. a. A set of linked genes or other genetic markers that are generally inherited together as a unit. This occurs because during meiosis there is little or no recombination with the corresponding region on the homologous chromosome, and hence shuffling of alleles between the homologous regions is rare. The stretch of DNA containing a haplotype is called a haplotype block. For example, the genes of the major histocompatibility complex in humans are closely linked at the HLA locus on chromosome 6 and behave as a haplotype, with the alleles on maternal and paternal chromosomes generally transmitted to offspring in the same combinations. Levels of recombination differ in different parts of the genome, causing the phenomenon known as linkage disequilibrium, which means that haplotype blocks are more likely in some genomic regions than in others.

2. b. The entire set of genes occurring on a single chromosome, or haploid set of chromosomes. Hence an individual has two haplotypes for each chromosome, one derived from its mother and one from its father.

2. (in medicine)

1. a. The antigenic constitution of an individual (i.e. antigenic phenotype) resulting from the inheritance of a particular haploid combination of histocompatibility alleles at the HLA locus.

2. b. The set of phenotypic features associated with either the paternal or maternal alleles inherited by an individual. See also international hapmap project.