Haplotypes

A haplotype (haploid genotype) is a group of genes in an organism that are inherited together from a single parent. A haplogroup is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism mutation. passes along a maternal lineage that can date back thousands of years. There are, however, several specific definitions of the term being used in genetics. First, it is a portmanteau word for haploid genotype, which is a collection of specific alleles (that is, specific DNA sequences) in a cluster of tightly-linked genes on a chromosome that are likely to be inherited together—that is, they are likely to be conserved as a sequence that survives the descent of many generations of reproduction.

A second specific meaning of the term haplotype: a set of single-nucleotide polymorphisms (SNPs) on one chromosome that tend to always occur together, i.e., that are associated statistically. It is thought that identifying these statistical associations and few alleles of a specific haplotype sequence can facilitate identifying all other such polymorphic sites that are nearby on the chromosome. Such information is critical for investigating the genetics of common diseases; which in fact have been investigated in humans by the International HapMap Project.

Another specific definition of haplotype: Many human genetic testing companies use the term 'haplotype' to refer to an individual collection of specific mutations within a given genetic segment; (see short tandem repeat mutation). The term 'haplogroup' refers to the SNP/unique-event polymorphism (UEP) mutations that represent the clade to which a collection of particular human haplotypes belong. (Clade here refers to a set of people sharing a common ancestor.)

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