Haplotype

A haplotype is a set of genetic variants on one chromosome that tend to be inherited together. It can identify a chromosome segment shared through ancestry.

Genetic variant: A difference in DNA sequence among individuals or chromosomes. Each haplotype is defined by the particular variants present on one chromosome.
Linkage disequilibrium: A nonrandom association of alleles at different genetic locations in a population. Nearby variants in a haplotype often show linkage disequilibrium because they are inherited together.
Genome-wide association study: A study that tests genetic variants across many individuals for association with a trait or disease. Associated haplotypes can mark genomic regions that contain variants influencing the studied trait.
Mutation: A heritable change in the DNA sequence. New mutations add variants that can become part of a haplotype.
Chromosome: A DNA molecule packaged with proteins that carries genetic information. Variants form a haplotype when they occur together on the same chromosome.
Genetic linkage: The tendency of genetic locations on the same chromosome to be inherited together. Physical proximity makes the variants in a haplotype less likely to be separated by recombination.
Genetic association: A statistical relationship between genetic variation and a trait in a population. A haplotype may associate with a trait even when its causal variant is unknown.
Genetic drift: Random changes in allele frequencies across generations, especially in small populations. Drift can raise or eliminate haplotypes independently of their effects on fitness.
Allele: One of two or more alternative forms of a genetic sequence at a particular location. The alleles at multiple locations together distinguish one haplotype from another.
Haplotype phasing: The process of determining which genetic variants occur together on each homologous chromosome. Phasing assigns observed variants to the chromosome-level combinations called haplotypes.

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