Terms genomic selection

Base

A component of DNA. DNA contains four different bases: Adenine (A), Cytosine (C), Guanine (G) and Thymine (T). Together the four bases form the alphabet of the genetic code.

Base Pair

Im Doppelstrang der DNA treten die vier Basen immer als Paar auf: Adenin (A) mit Thymin (T), Cytosin (C) mit Guanin (G).

Chromosome

Structure in the cell nucleus that contains the genetic substance (DNA). Chromosomes occur in pairs apart from in gametes and originate half from the father and half from the mother. In cattle there are 2 x 29 normal chromosomes in addition to the two sex chromosomes.

Direct genomic breeding value

Breeding value that is exclusively estimated using marker information (SNP).

DNA

Abbreviation of the term DesoxyriboNucleic Acid. A thread-like molecule in the cell nucleus in the form of a double-strand. DNA contains the genetic code.

Gene

One section on the DNA strand, which contains the coding for forming a protein.

Genome

Entirety of genetic substance (DNA) in one cell nucleus.

Genomic optimized breeding value

Breeding value that was estimated using traditional information and marker information (= combination of the traditional breeding value and the direct genomic breeding value)

Imputing

A statistical procedure with which a genotype is projected from a lower to a higher density, for example from 6,000 SNPs to 54,000 SNPs. This takes advantage of the fact that chromosome sections are transferred in pieces from parents to their progeny.

Marker

In microbiology this is a short section on the DNA molecule at a known position which can be determined unambiguously.

QTL

Abbreviation of Quantitative Trait Locus
The location in the genome which has a detectable influence on the manifestation of a quantitative trait. Very often the precise location in the genome is unknown.

Qualitative Trait

A trait that only occurs in a few manifestations. Examples: Colour (red/black), horns/ polledness.

In contrast to quantitative traits, a qualitative trait is controlled by only one/a few genes and in a normal case is not influenced by the environment, or only slightly.

Quantitative Trait

A trait that occurs in continuous form, for example body size, weight.
In contrast to qualitative traits, a quantitative trait is mainly influenced by many genes and also by the environment.

SNP

Abbreviation of the term Single Nucleotide Polymorphism, pronounced Snip.
Variation relating to an individual base pair on a specific location of the DNA strand. Occurs very frequently in the genome (cattle: more than 1 million known locations) and is well suited as a marker as it can be determined in large numbers in the laboratory with an SNP-chip. 

SNP-Chip

Chip through which in the laboratory a sample of several thousand or even hundreds of thousands of SNPs can be determined with high levels of precision, relatively cost-effectively and quickly.

Standard currently for cattle is the Illumina® BovineSNP50 Genotyping BeadChip, with which over 54,000 SNPs were determined simultaneously on 12 samples.

Confidence interval

A statistical term which indicates in which range around an estimated value the unknown true value is located. The smaller the confidence interval, the more accurate the estimated value.

With a confidence interval a probability must always be indicated. Customary is a confidence interval of 95% which states in which range in 95 of 100 cases the true value is located.