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title: "4.15.2 Marker assisted selection for monogenic traits (2024)"
canonical: "https://wiki.groenkennisnet.nl/space/TAB/287605282/4.15.2%20Marker%20assisted%20selection%20for%20monogenic%20traits%20(2024)"
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The second application of a genetic marker is the tracing of alleles with a favorable effect in marker-assisted selection. Only a few genetic markers were found in production animals that were closely linked to a QTL with a favorable effect. Therefore the use of markers in selection was limited until genomic selection was introduced. In Salmon the infectious pancreatic necrosis virus (IPNV), may lead to significant levels of mortality. Across salmon populations a QTL was found that has an allele that gives a significant reduction in numbers of IPN cases in Norway and other salmon producing countries.
The third application of a genetic marker is the tracing of alleles with an unfavourable effect. First rate examples are monogenic recessive genetic defects that are present in all species. The next table gives an overview of the total number of recorded genetic defects per species, the disorders that are monogenic recessive traits (Mendelian trait), the disorders from which the mutation in DNA is known and for which a genetic marker available and the number of genetic defects that can be used to study human diseases:
Genetic markers for monogenic recessive traits are very valuable, because they can be used to detect the heterozygote carriers of the allele, heterozygous animals that do not show any symptoms of the genetic defect but do transmit it to 50 per cent of their offspring. The mating of two heterozygous animals gives with a chance of 25 per cent offspring that is showing the symptoms of the genetic defect.