Paternity Test Archives - Page 41 of 54

He’s Not the Biological Father? Why are there Matches in the Paternity Test?

by HOMEDNA on 01/31/2011

After DNA samples arrive at the laboratory, IDENTIGENE paternity test results are released in two business days. And they may not always be what are expected!

Sometimes when results of DNA testing show 0% probability, meaning the alleged father is not the biological father, there are some loci (or markers) in the report that do match between the alleged father and child. Participants may not understand why this occurs in DNA testing if the two participants aren’t related, so here’s a quick overview of how this happens.

Basics of a DNA Paternity Test

In paternity testing we generate DNA profiles using Polymerase Chain Reaction (PCR) process. PCR is the process of taking a small piece of DNA and making many enlarged copies so it can be measured for a paternity test. In the DNA profile analysts look at 15 specific loci or markers (location on the DNA chromosome for a gene) which are then reported on the DNA test results. The profiles are compared for all participants to determine if the alleged father and child match at all 15 markers or locations. Because the child gets 50% of its DNA from the biological father and %50 from the mother, there must be a match at all loci for the alleged father to be considered the biological father. If there are any mismatches, then the alleged father will be excluded, even if there are a few matches.

Loci Matches on Paternity Tests

A few positive matches can happen in DNA paternity testing because there are specific markers that are common among the population. When you look at the profiles on a paternity test, and there are some matches, this does not necessarily mean the participants are related. Each matching loci between the alleged father and child is calculated into a paternity index which measures the strength of a genetic match. This indicates how common that marker is in the population. Sometimes markers are very common so people that are not related may match at certain locations.

As stated above, in order to be a biological parent there must be a match at each location (with the rare exception of one mutation, which is a change in a gene passed from parent to child). If a possible mutation is identified, additional markers will be tested.

This is why you may have some locations that match on a paternity test but paternity test results nevertheless indicate the alleged father is not the biological father.

Can’t I Just Use Cotton Swabs to Collect DNA Testing Samples?

by HOMEDNA on 01/27/2011

DNA is considered to be the blueprint of life, and a DNA test can help determine biological relationships by using paternity other types of DNA testing. Collecting DNA for a paternity test is much less invasive than it used to be. Instead of having to draw blood, cheek (buccal) swabs are used in DNA testing. You just swab the inside all participants’ cheeks and then send the samples in to the lab.

Can “regular” cotton swabs be used for a paternity test?

One of the most common questions addressed to the IDENTIGENE Client Support Team is: Why can’t people just use cotton swabs and send those in instead of using the cheek swabs included in a DNA test collection kit?

The DNA testing swabs are like cotton swabs, but with some very important modifications. The tips are made from a special Dacron polyester material that is optimal for DNA collection and extraction of the DNA in the laboratory. This material effectively captures the cells needed for paternity testing and holds on to them.

Although DNA for paternity testing can (in theory) be collected on regular cotton swabs, the process for extraction of the DNA is much more difficult and less reliable than extraction from the special Dacron swabs supplied in the DNA collection kits. Because of this, samples submitted on regular cotton swabs are considered ‘special specimens’and the cost for testing is higher due to the extra work involved.

Follow us on Facebook and Twitter! If you have questions about paternity tests or other DNA testing services, please contact our Client Support Center at 888-404-4363, Mon-Fri from 9 AM to 6 PM Eastern Time. Our friendly, expert representatives are ready and happy to help. Get answers anytime by visiting our Help Center.

Do I Need to Include Mom in a Paternity Test?

by HOMEDNA on 01/25/2011

Nearly all DNA paternity test results can be reported accurately without the biological mother participating, but including her in the paternity test can strengthen the results in some instances. That’s why we strongly recommend that, whenever possible, the mother should be included in DNA testing.

How does including the mother help in paternity testing?

DNA paternity testing analyzes 15 Loci or markers (locations) on the DNA to determine if there are matches between the alleged father and the child at each location. If there are matches, each match receives a paternity index value which is used to calculate the combined paternity index and gives the probability of paternity (usually 99.99% when the alleged father is included as the biological father, or 0% if he is excluded).

Most paternity tests with only the alleged father and child participating do show conclusive results, meaning we have enough information to report conclusively or simply put, a yes or a no answer. There are occasions when the matches between the alleged father and child are inconclusive. This happens when the calculations involved could not get the probability of paternity above 99%, although there are matches. If this does happen, Identigene will ask for the biological mother’s sample to be included in the paternity test. If the mother is not willing or is unavailable, the results will remain inconclusive. Including the mother almost always gives conclusive results. We strongly recommend including the biological mother in any DNA test, including grandparent, avuncular, and sibling DNA testing.

Why Test the Mother?

Here is an example that we use to demonstrate how the mother’s profile helps strengthen paternity test results:

Locus	Biological Mother (not tested)	Alleged Father	Child	Parentage Index
D2S1338	—	12, 13	10,12	1.845
D2S1358	—	8,11	11, 14	2.714
D8S1179	—	21.2, 32	19, 21.2	2.675
D19S433	—	15, 18	12, 15	7.338

In this case, the probability of paternity is 98.2896% (the product of all the parentage indexes). The result is inconclusive because probability of paternity must be greater than 99% or at 0% to be conclusive, yet the alleged father and child match at all locations. Now, add the biological mother’s sample to the DNA paternity test:

Locus	Biological Mother	Alleged Father	Child	Parentage Index
D2S1338	8, 10	12, 13	10, 12	3.489
D2S1358	14, 17	8, 11	11, 14	5.114
D8S1179	15, 19	21.2, 32	19, 21.2	3.619
D19S433	8, 12	15, 18	12, 15	15.309

In the second table, the paternity index is increased and the probability of paternity increases to 99.9541%. Why? In the first example, one of the two markers from the child and alleged father match at each location. However, we don’t know which of the child’s markers comes from his mother and which must come from his father. By testing the child’s mother, we see which of the child’s markers must have come from the father.

Not only does the child match the alleged father, but the match is with the marker that must have come from the child’s true biological father (since we can see which marker came from the child’s mother). In fact, the index value is higher at each location because the biological mother participated in the DNA test.

If you have questions, don’t hesitate to call IDENTIGENE’s Client Support Team during business hours at 888-404-4363.

How does including the mother help in paternity testing?

Why Test the Mother?

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