Definitions

allele: One of several alternative forms of a gene that occur at the same locus

coding SNP: An SNP located with protein coding sequences

genotypic relative risk: The ratio of the probabilities of individuals carrying a specific genotype to those carrying a different genotype for developing a specific phenotype

genotyping: Determining the alleles for a locus on the two chromosomes of each of a set of individuals

haplotype mapping: A method of mapping using a set of alleles that are in linkage disequilibrium

HapMap: A map showing the haplotype diversity and extent of linkage disequilibrium in the genome

linkage analysis: A recombination-based method of determining the location of a gene

linkage disequilibrium: The tendency of closely spaced alleles to be correlated

linkage peak: A chromosomal region that shows linkage with a specific phenotype

net genetic contribution: the contribution to disease of genetic factors once shared environment has been removed

relative risk: the increase in the probability of expressing a phenotype (e.g. a disease trait) for a given genotype compared to the wildtype (non-predisposing) genotype

Single Nucleotide Polymorphism (SNP): A position in the genome where some individuals have one base (for example, A) and others have a different base (for example, C)

Transmission Disequilibrium Test (TDT): A family-based test of allelic association