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TechnologyClear-cut parentage control using microsatellitesIn animal husbandry law and the breeding regulations of the herdbook associations, and the horse- and dog breeding associations as well, the parentage verification is part and parcel of the internal control of the farming accounts. For example, besides random control, all cattle, which stem from embryo transfers, are routinely parentage controlled. Of course, a corresponding control is carried out on all prized breeding animals, e.g. in horses. The out of date practice of bloodtyping achieves only an exclusion probability of 90 - 95%. This means that from statistical view, only 90 - 95 of 100 wrong assumed parents can be excluded from parentage, in fact.
 In contrast, the DNA-based method of genotyping using microsatellites is the most economical and reliable state of the art method of animal identification and parentage verification. By analysing microsatellites (markers) a genetic profile of an individual is determined, often called "genetic fingerprint". If one compares the DNA-profile of the offspring with these of the putative parents, the parenthood can be verified with an exclusion probability far in excess of 99%. DNA-microsatellites as markersThe genome is composed of four components: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Microsatellites consist of identical, multiple reiterating sequence patterns (e.g. ...CACACACA..., one of the most frequent patterns), which are dispersed over the complete genome without being coding for any genetic trait. The number of the repeating units varies from individual to individual, which is the prerequisite for the suitability as markers:The combination of the particular sizes of the respective markers identifies the genotype of an individual. These differences in the sizes of the respective markers are used in several species (presently horse, cattle, pig, sheep, and dog) in determining the identity of an individual or the respective parenthood. For example in horse breeding, in combined testing of twelve markers a mean exclusion probability in exces of 99,9% is achieved. Because of their standardization, these twelve markers are internationally reproducible and exchangeable on client's request between the respective labs, which also operate according the internationally acknowledged standards. 
 Determination of genetic defects or special genetic traitsBesides identity- and parentage tests, DNA-tests can provide further valuable, relevant information to the breeder. In almost all fields of animal husbandry, recessively (disguised) inherited genetic defects are a well-known problem. Only in the case when these defects are homozygous, a disease can be diagnosed directly. Heterozygous animals are phenotypically inconspicuous and remain undiagnosed, which may lead to the dispersal of the genetic defect over the whole population. In the case that the knowledge exists, on which chromosome and on which locus the hereditary disease is localised, the carriers can be identified definitely and excluded out of the breeding programme. At least, the risk is minimised to breed homozygous, afflicted animals by DNA-diagnostics. In animal husbandry genetic tests are engaged in practice for years, in order to test, whether valuable breeding animals are carriers of recessive hereditary diseases.In the same way, desired genetic characteristics, e.g. traits which account for a particular milk-quality, can be tested in potential breeding animals. Furthermore, an increasing number of tests is available, which determine the hereditary disposition for the different coat colours, which allow a quite wide prediction of the coat colour of the animals which are going to be bred. The so-called gene-tests rely on the fact that the hereditary disposition, which is going to be tested, is altered (mutated) in one component. Once the mutation is reconnoitred, which may need several years, the mutation can be determined directly in an enzymatic reaction: in today's biotechnology, a large number of enzymes is available, which recognise particular DNA-sequences and cut the DNA at these positions in a particular way. For example, it is common laboratory practice, to multiply the DNA-fragment, which is going to be tested, in an enzymatic reaction, and in an subsequent, second enzymatic reaction it is checked, whether the respective mutation is present, i.e. the fragment is cut in two or more pieces. More modern, technically challenging methods make the sequence of two independent enzymatic reactions unnecessary. Because the methods are fairly complex, we refer to the corresponding literature regarding SNP-diagnostics. see also: contact Accreditation |
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