DNA Vaderschap

 


Frequently Asked Questions (FAQ)


What is DNA?
DNA carries our hereditary information. It is present in most cells of every multicellular organism. It is in fact a very long sequence of nucleotides, the building blocks of DNA. In DNA we find 4 different nucleotides (base pairs).
Just like digital information is represented as a sequence of zeroes and ones, genetic information is represented by a sequence of nucleotides.

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How does a DNA paternity test work ?
Every person has two copies of each gene. One copy comes from the mother and the other copy comes from the father. Thus, one half of the genetic material in our body is inherited directly from each of our two parents. When a DNA- paternity test is performed, our DNA laboratory examines the DNA of the child to determine whether the father's contribution matches that of the alleged father. If the alleged father is the true biological father of the child, half of the child's genes will match that of the alleged father's. The other half comes from the mother and will match the profile of the mother (testing the mother is optional). If the tested man is not the biological father of the child, the half of the child's genetic material which comes from the father will not match the DNA-profile of the tested man. If the DNA-profile does not match, the tested man is excluded as being the true biological father of the child. When a DNA paternity test is performed, the laboratory usually examines many different genetic locations. The more genetic locations that are examined, the more powerful and accurate your test becomes. After examining many genetic locations, a DNA lab can conclusive determine whether the tested man is indeed the true biological father of the child. Our paternity test report will provide you with a simple "yes" or "no" conclusion for your paternity test as well as a detailed report indicating the DNA-profiles of each tested individual.

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How can people be identified on the basis of their DNA?
Most living organisms grow from one cell —the fertilized egg cell—, which by multiplying itself eventually gives rise to all cells that make up the adult individual. Roughly one could say that every cell of an individual contains the same genetic information, i.e., every cell of a multicellular organism has identical DNA content.
However, the DNA content of different individuals is (slightly) different.
When DNA from separate individuals is compared, discrepancies can be found. These discrepancies can be used to determine the relationship between those individuals.
Similarly, when samples have identical DNA contents, they must come from the same individual.

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What is a genetic locus or marker?
Since it is not possible to analyze all of a person's DNA, in practice, specific genes are selected for analysis. These genes typically do not code for any physical property of the individual, but are chosen for their properties of being easily analyzed and having a high discriminating power in identification and consanguinity analysis.
A genetic marker is a piece of DNA (or a gene) that everyone has, but that can, in each individual, be one of a few different forms that occur in the population (alleles). The pattern of alleles that a person carries for set of genetic markers is called a DNA profile.

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What is a DNA profile?
The pattern of alleles that a person carries for set of genetic markers is called a DNA profile or a DNA-fingerprint. A DNA profile is similar to a real fingerprint in that its pattern is unique for each individual and hence can be used to unequivocally identify an individual. DNA profiles are comparable only if they describe the same loci. Comparison of genetic fingerprints can yield information on consanguinity because each half of our genotype for every genetic markers is inherited from one parent.

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What is the "matching probability"?
The matching probability is a value that is given to the chance of a false positive identity match when comparing two DNA profiles. The more genetic markers that are compared, the smaller the chance of a false positive match.

To clarify this concept, we present a simple example.
If one were to investigate locus A whose variants A1 A2 A3 A4 and A5 (=alleles) occur with equal probabilities (1/5) in the population, then comparison of two samples may show that these samples match. That means they contain the same set of alleles and both samples may be from the same individual. Assume that the matching samples each contain the A1 and A2 alleles for the A gene. Knowing that any allele of the A gene has a one in five chance of being A1, the frequency that the A1A2 genotype will occur in the population is the product of (the chance that A1 will be one of 2 alleles) and (the chance that A2 will be one of 2 alleles). The chance that A1 will occur in any two alleles tested, is calculated as (2X(1/5)-(1/5)^2)=36% . The chance of A2 being in-there is the same (36%), since the population frequency of A2 is 1/5 also. The chance of finding both A1 and A2 in any two alleles analyzed for the A gene is therefore 36%X36%=12.96%.
All this means is, that when you find the genotype of a person for gene A to be A1A2, the chance that you will match this profile with a sample from any random individual, is about 13%.
If in addition a locus B is investigated, whose variants B1 B2 B3 B4 and B5 are also uniformly distributed, then the chance that two individuals carry two matching genes is reduced to 1.6%. With 3 loci this probability is only 0.2% and with 4 loci it is 0,03%. with 15 genetic markers, it is 4.9e-14.

This example is somewhat simplified in that the variants of a gene are not equally frequent, and there are usually more than five variants. The standard STR loci that are used for identification are chosen for their high discriminating power. The matching probability of an identity profile with the 13 codis markers, D16S539, D2S1338 and amelogenin is no more than 1 in 50 billion, which is astronomically small. The chance of a cosmic ray changing a DNA profile when it is being processed by hitting the RAM of a computer, is probably higher.

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What are STR analyses?
STR stands for Short Tandem Repeats or short equally oriented repetitions in the DNA sequence. STR loci are loci whose alleles differ in the number of repetitions of successive base pairs, which makes them easier to distinguish because the difference between two alleles is an integer multiple of the length of the repetition. The loci that are in standard use in the forensic world and that are used in the big DNA databases of international law enforcement agencies and the FBI, are all STR loci.

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How much DNA is required for a successful analysis?
All we need is 0,5 ng, i.e., half a billionth of a gram DNA. That's a very tiny amount!

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What is a sample kit and how do I obtain a sample?
You may order a kit using our web form, or by telephone at +32-485-471309.
The kit contains everything you need to take one or more samples under optimal conditions. These should then be forwarded to us.

I have a hair/cigarette but/stain/... that needs to be analyzed. What now?
If you already have our sample kit, just follow the enclosed instructions and put the sample in the tube, label the kit and mail it to us.

Make sure that you are familiar with the legal issues concerning privacy, in particular which approvals are needed for obtaining samples from each individual (Further considerations...).

Take care to protect the sample as much as possible against contamination with other human DNA. Try, in the mean time, to keep the sample dry, to prevent bacterial breakdown of the human DNA. Use clean tweezers to insert the sample in the vial.

The cotton swab serves to take a sample from e.g., you can obtain cells from the mouth, by rubbing the swab a few times vigorously against the inside of the cheek. Then put the swab, cotton end first, in the vial and use scissors to cut any excess length such that the vial can be closed.

If you send hairs, try to include the follicles.

After shutting the vial, label the sample with a reference number of your choice (use the label provided with the kit). If necessary use transparent adhesive tape to fix the label.

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How soon can the analysis results be available?
Under normal circumstances you will receive the results from the DNA analysis within a week after our receipt of the samples. The limiting factors here are the quality of the samples and the capacity of the lab equipment.

Express Service
We can't guarantee a maximum turnaround time, but in urgent cases, and with good quality samples results can be available within 48 hours after receipt of the samples. The surcharge of 200 Euros for express service is to compensate for suspending and restarting the lab's workflow. If we don't make the 48 hours, there will be no surcharge.
Call us at +32485471309 to discuss how to most efficiently get the samples to the lab.

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What kinds of samples can be analyzed?
In principle, anything that contains human cellular material, even a smear or a smudge, can be used. To take a sample in ideal conditions, it is best to use a cotton swab or Q-tip and rub it gently on the inside of the cheek and under the tongue (cf. the sample kit for the parental testing)

Even traces of DNA (very small quantities) are sufficient for a successful analysis. A post-stamp that was licked will usually contain sufficient amounts of saliva to contain human cellular material. A cigarette but, a toothbrush, the stick of a lollipop, a dummy teat, a razor blade, a stain on underwear, scales of skin from a sheet or pillow case, a used handkerchief, a worn garment, a used condom, 0.1 ml of urine, a blood stain on paper or cloth are acceptable as well. These are all examples of samples that can yield DNA profiles and can serve for identification or kinship analysis.

Hair should have hair roots. A single hair root may not contain enough DNA for analysis. Just like hair shafts, fingernails contain very little or no DNA.

It is important to know that the situation gets more complicated, and more difficult to interpret, when DNA from different people is present in a single sample.

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How long will a sample retain its quality?
DNA is quite stable, and, under most circumstances can be stored for a long time with no degradation. It is always a good idea to keep samples dry. Humidity can cause bacteria and fungi to grow, and consume human DNA traces.
So send your samples quickly, or dry them first!

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