Glossary

CONFOUNDING: not correctly measuring the relationship between two things due to the influence of other factors, which affect the result but which have not taken into account.

GENE: a primary functional element of the genome, commonly defined as something, which when transcribed and the resulting mRNA is translated, results in the production of a protein. This definition is not universally applicable, however, and other non-genic functional elements are recognised to exist in the genome.

GENETIC MAPPING: also known as linkage mapping, this relies on the genotyping using known polymorphic (variant) markers to calculate the frequency of times pairs or triplets of particular polymorphisms co-occur. This relies on the phenomenon of recombination to shuffle particular pairs of markers apart, which is more likely to occur when they are more distant from each other. Maps are constructed on the basis that a higher frequency implies closer proximity, though these are based on relative relationships rather than absolute distances.

GENETIC MARKER: a small part of the genome that exists in different forms and variants that can be identified and mapped using a range – and usually combination – of quantitative, classical and molecular genetic techniques. Genetic markers include Single Nucleotide Polymorphisms (SNPs), Restriction Fragment Length Polymorphisms, microsatellites and minisatellites.

GENOMIC SELECTION: method of genomic prediction that uses genotypic data on a large number of markers (Single Nucleotide Polymorphisms) and phenotypic data on a significant number of organisms to create a prediction model that can be used to estimate (for example) breeding values of livestock animals.

GENOTYPE: the genetic constitution of an organism.

HAPLOTYPE: a particular combination of genetic variants that may be exhibited in one or more organisms. Different haplotypes imply different phenotypic outcomes.

LINKAGE MAPPING: see GENETIC MAPPING.

MAPPING: the procedure of identifying the relative or absolute positions of particular landmarks – markers – in the genome. The two main forms are physical mapping and genetic (or linkage) mapping.

MICROSATELLITE: a kind of genetic marker, featuring repetitive sequence with patterns of under 10 base pairs being repeated dozens of times.

MINISATELLITE: a kind of genetic marker, featuring repetitive sequence with patterns of over 10 base pairs being repeated up to 10 times.

OUTBRED: in the case of humans, this means potentially comprising ethnically diverse individuals.

PHENOTYPE: the measurable outcome of development and physiological processes in organisms.

PHYSICAL MAPPING: set of genomic mapping approaches that involve the localisation of markers to specific places in the genome. These approaches include Fluorescent In Situ Hybridisation, Radiation Hybrid mapping, and fingerprint mapping.

POLYMORPHISM: a difference in DNA sequence between individuals.

RESTRICTION FRAGMENT LENGTH POLYMORPHISM: a kind of genetic marker, produced through the cutting of specific sections of DNA using restriction enzymes. Different variants mean that the length of fragments produced as a result of this enzyme action also varies.

SINGLE NUCLEOTIDE POLYMORPHISM: a variant at the level of the DNA base or nucleotide.

SNP CHIP: a tool – a kind of microarray – that enables the presence or absence of particular Single Nucleotide Polymorphisms to be recorded for the purposes of genotyping.