Spacer Corner Spacer Spacer
FAQ faq
Sitemap sitemap
Careers careers
Contacts contacts
Corner Spacer
Medical Genomics Medical Genomics
Spacer Corner
Spacer Spacer Spacer

how does DNA testing work?

Paternity (maternity) testing

DNA testing relies on comparing fragments of DNA (called “genetic loci” or simply “loci”) between an alleged parent and a child. A child receives one half of his DNA from the mother and the other one from the father moreover, the process is more or less random. This means that approximately half of all genes  between a parent and his/her child are identical. If we compare a fragment of DNA between an alleged parent and the child it has a 50% chance to be identical. If we compare 12 different fragments, then, according to statistical laws approximately 6 of them will be identical. In such a case the probability that the alleged parent is a true biological parent of the child will be 99.99%. In contrast, if none or 1-2 of the loci studied turn out to be identical, then the probability of the individual being a true biological parent of the child is no higher than for any other person on the street, meaning that he/she is biologically unrelated to the child.

Two factors affect the accuracy of testing – the number of genetic loci tested and their nature. More then 99% of DNA is identical between all people and if it was analysed there will be no difference found between any two individuals, men or women, randomly taken. However, there are certain areas of DNA which are unique for each individual (this is to a large degree what makes people different) or found only in a small number of individuals. Among those, areas of highly variable DNA called STR or simple tandem repeats are the ones which are commonly used for DNA testing and people identification. All this means that the more  genetic loci (like STR) are checked the higher will be the probability of confirming paternity or maternity. Medical Genomics is currently analysing 16 STR loci for each DNA sample, which gives us a probability of 99.9999% in confirming alleged paternity (maternity).

Close Relative Testing (Grand Parent/Uncle/Aunt/Niece Nephew)

There is no difference in the testing procedure between this type of test and paternity (maternity) testing. The only exception is that in order to achieve a reliable accuracy more genetic loci have to be compared. This is because a grand parent shares only 25% of his/her genes with an alleged grand child, uncle and aunt also share 25% of their genes with the alleged nephew/niece (this is assuming, of course, that they are not twin brother/sister of the person in question’s father or mother and also that they are all from the same parental line) etc. Taking example from the above section, out of 12 loci analysed approximately 3 should be identical between an alleged grand child and the grand parent.

Half Siblingship/Full Siblingship Testing

Full siblings obtain DNA from the same mother and father and have most of it in common, though there will be slight variation in the genes they inherited from a particular parent. In contrast, half siblings will share only 50% of DNA in common. By analysing DNA from two individuals it will be possible to unambiguously conclude whether they are half or full siblings.

Twin (Zygosity) Testing

Twins can be of two types – identical, born when the egg divides into two separate cells straight after being fertilised by a single sperm and each cell then develops into an embryo, and fraternal, which are produced when there happened to be two eggs in the womb which are fertilised by two sperms. Identical twins are always of the same sex, have absolutely identical DNA and it is impossible to find any genetic difference between them (they are virtually clones of the original fertilised egg). Fraternal twins not need to be of the same sex and have minor differences between their DNA. Using state of the art DNA analysis of highly variable STR loci Medical Genomics is able to determine whether two individuals are identical or fraternal twins.

Y-Chromosome Testing

Y-chromosome is transmitted by fathers to their male offspring only. It is highly variable between human population and by analysing fragments of Y-chromosome from two or more male individuals it is possible to determine whether they all share the same male ancestors, how close is this relationship and are they all part of the same family (so called “surname test”). This analysis is commonly used for genealogical purposes. Being at the cutting edge of high-tech genealogical research Medical Genomics compares 26 STR found on Y-chromosome and gives a conclusive report on whether two (or more) male individuals are related and how close is the relationship.

mtDNA Testing

People inherit mitochondrial DNA (mtDNA) from their mothers. This is a convenient tool for studying human migration patterns, evolution, maternally linked relationships and people identification. Mitochondrial DNA has two highly variable regions, called HVR-1 and HVR-2. Medical Genomics determines the structure of HVR-1 in all individuals in question and then compares the results to the generally accepted standard - the Cambridge Reference Sequence. This analysis allows us to give a definite and conclusive answer whether the individuals tested are related, belong to the same ethnic group and to the same maternal genealogical group.
Spacer Spacer
MG MG Spacer
Spacer Spacer
Corner passion creation by ehouse`interactiveSpacer