Following the interest in our first newsletter in August we have decided to produce a second one.
November is usually the time of the year when the VGL, similar to other entities, focuses on finalising
current projects and plans for the next year. Throughout the year, the laboratory has received a number of requests about the value of the DNA certificate and the DNA profile, parentage testing, colour variant testing in wildlife, sample collection for DNA profiling and individual animal identification and traceability systems and how this all relates to improving breeding of these animals. We have addressed a few of these queries in brief in this newsletter. We hope that these short explanations will be helpful. As always we encourage feedback and questions that we could discuss in the future newsletters as well.
Mitochondrial and nuclear based DNA tests
There are two types of DNA in cells: nuclear DNA, which is found in the cell nucleus (core) and
mitochondrial DNA, which is found in the mitochondria in the cell body. Mitochondrial DNA (mtDNA) is derived from the mother who provides the cell body. This DNA is used most often in forensic science to identify the species of animal from which an unknown piece of tissue is found. A short (400 to 700 base pair) section of the mtDNA is sequenced in an unknown piece of meat, tissue or material and the sequence compared to sequences from known animals that are stored on Genbank. Genbank is a collection of publicly available sequences of many species uploaded by scientists from all over the world. It is managed by the National Centre for Biotechnology Information. A match of the sequence of the mtDNA of the unknown sample to a sequence on Genbank of a known animal provides the identity of the unknown
The mitochondrial DNA is also used for subspecies testing. Testing to differentiate the subspecies of sable and roan are most often requested, where the mtDNA sequence is used to identify the geographic origin of a specific animal. Since mtDNA is only inherited from the mother, this test only reflects the maternal contribution to an individual. The Veterinary Genetics Laboratory does not perform this subspecies testing but refers breeders to the most appropriate laboratory who will do this testing for them. Certificates that contain the subspecies test result can also only be obtained from the testing laboratory directly and not
from the VGL.
Nuclear DNA, which is found within the nucleus of the cell, is packaged in structures called chromosomes. Chromosomes occur in pairs, the one representing the genetic contribution from the father and the other, the mother. Short fragments of repeated DNA code of variable length, or microsatellite markers, are used to compile an individual DNA profile. The DNA profile is unique to an individual and can be used as positive and irrefutable identification of the individual in forensic cases or can be used to confirm the parentage of an individual.
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Last edited by Gideon van der MerweEdit