All About Paternity Testing

According to the American Association of Blood Banks, there were 354,011 reported parentage testing cases, translating into approximately 991,000 individuals being tested. This was a 3.9% increase over the previous year. With so many people taking parentage tests, it is important to understand the implications. Here we focus on paternity testing.

What is paternity testing?

Paternity testing is DNA analysis to determine whether or not a given man is the biological father of a given child.

Why would I want paternity testing?

There are many different reasons people want to have a paternity test. Sometimes alleged fathers are told many years later that a previous relationship resulted in the birth of a child, and they want to make sure they are actually the biological father. Some men might suspect their wives or girlfriends of infidelity and are concerned their child may not be theirs biologically and want the peace of mind a DNA test can provide. Children who were separated from their biological father at a very early age, whether because of adoption or other reasons, often want a conclusive DNA test early in the reunion process. Children sometimes learn about infidelity after the death of a parent and are curious about their genetic makeup and their family's medical history, so they have DNA tests to prove their parentage.

More and more we hear about court cases involving DNA paternity testing. Child support cases have been much more prominent in recent years than ever before, and DNA is being used to support or rebut child support claims. A California case brought national attention to the issue last year when an appellate court reversed a trial court ruling that a Los Angeles man had to financially support two children to whom he had no biological relationship.

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How are the DNA samples collected for the paternity test?

The collection process is very simple and does not cause any pain. Most companies now perform paternity testing using simple buccal swabs because DNA is found in all cells in the body. You rub the buccal swab on the inside of the cheek of your mouth. Then you place the swabs in the container provided to return them to the laboratory. And that is all you have to do complete the sample collection.

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What if there are two alleged fathers who are related?

Since family members are more likely to have similar genetic profiles, when two alleged fathers are related, the probability of paternity may be lower than in standard tests. In such cases it is always best to test both alleged fathers, since the one who is not the biological father can be excluded with certainty. If the two alleged fathers are identical twins it is not possible to identify the biological father because identical twins have identical DNA profiles.

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How is paternity tested in the laboratory?

A cheek cell sample must be submitted from both the child and the alleged father in order to perform DNA analysis. You can do this in the privacy of your own home using the private paternity option we provide. Most companies prefer to have the mother tested, if she is willing and able, but it is not necessary because laboratories can generally get the same conclusive results as they would if testing a standard trio (mother, alleged father, and child).

Once all the specimens reach the laboratory, the testing process can begin. There are others, but the technology used most often is the Polymerase Chain Reaction (PCR) testing for analysis. First, pure DNA is isolated from the sample by removing all the proteins and other things that can be found within a cell.

Next, the laboratory examines specific loci (locations) of each individual DNA sample. Since all individuals have 2 copies of each chromosome, they will have two readings for each locus tested. Once testing is completed, DNA loci are compared. Readings for each tested individual will have two numbers. For each locus, one of the child's numbers must match one of the mother's numbers for that locus. The child's other number will match the biological father's.

One example of a standard trio (mother, child, alleged father) for one locus is as follows:

If the Mother=(1,2) and the Father=(3,4),

then the Child can be (1,3) (1,4) (2,3) or (2,4)

If the numbers match, a paternity index will be determined. The paternity index is a calculation of how frequently that match occurs in a specific race population, the likelihood that the tested man is the biological father based on that loci. One locus is not enough to conclusively determine paternity, so most labs test multiple loci. Look for a company that tests at least 16 different loci, including the 13 CODIS loci.

Each locus has its own paternity index. If all the loci match, the paternity indices for each are combined, and a probability of paternity is calculated. The probability of paternity is the final percentage calculated.

If the tested man does not match the tested child on a locus, the paternity index for that locus is 0. If there are 1 or 2 non-matches, examine the samples further to obtain conclusive results (additional testing of up to 25 total markers). If there are 3 or more non-matches, we conclude that the tested man cannot be the biological father of the tested child. The probability of paternity is 0%.

Look for a company that provides inclusion probabilities of at least 99.99%. Read everything carefully because some companies say they provide probabilities of 99.99%, but they only guarantee 99% when you read the fine print. A guarantee of 99.999% means the tested man is 99.999% more likely than any other man in his race population to be the biological father of the tested child.

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What is PCR Testing?

PCR is an acronym for polymerase chain reaction. PCR increases the amount of DNA available from a sample for typing and analysis.

Within the DNA string, some areas are the same for all human beings (conserved, or constant). Other areas tend to vary from person to person (variable, or polymorphic). The variable regions are usually scattered among the conserved regions and are used in DNA testing profiles.

Most organisms naturally copy their DNA in the same way. The PCR mimics this process, except replication takes place in a test tube. When any cell divides, enzymes called polymerases make a copy of all of the DNA in each chromosome. DNA polymerase is also used in PCR to make copies of specific target strands.

DNA is made from four nucleotide bases, represented by the letters A (adenine), C (cytosine), G (guanine), and T (thymine). The A on one strand of DNA always pairs with the T on the opposite strand, and C always pairs with G. The two strands are said to be complementary to each other.

To copy DNA, the polymerase requires two additional components: a supply of the four nucleotide bases and something called a primer. DNA polymerases cannot copy a chain of DNA without a short sequence of nucleotides to "prime" the process, or get it started. So the cell has another enzyme called a primase that actually makes the first few nucleotides of the copy. This portion of DNA is called a primer. Once the primer is made, the polymerase can take over making the rest of the new chain.

There are three major steps in PCR. The first step in this process is to denature (unzip, unwind) the target genetic material in the two DNA chains of the double helix. This is done by heating the material to 90-96oC. As the two strands separate, DNA polymerase makes a copy using each strand as a template.

The primers cannot bind to the DNA strands at such a high temperature, so the vial is cooled to 55oC for the second step in the process. At this temperature, the primers bind or "anneal" to the ends of the DNA strands.

The final step of the reaction is to make a complete copy of the originals. The specific polymerase that is used for this process works best at around 75oC, so the temperature of the vial is raised one more time.

The three steps in the polymerase chain reaction - separation of the strands, annealing the primer to the template, and synthesis of new strands - take less than two minutes. At the end of a cycle, each piece of DNA has been replicated.

The process can be repeated to get more of the targeted DNA; the process can be repeated using the DNA that was replicated in the first procedure. The total amount will double every time.

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What does "accuracy" mean?

Accuracy literally means "free from mistake or error." Do not get this confused with probability, meaning "likely to be true or real."

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How do I read the results of my paternity test?

A formal paternity test report contains information about the different loci analyzed to generate the paternity result. The section you will want to focus on is the Probability of Paternity at the bottom of the report. This value will fall into one of two categories:

Inclusion: A probability value of at least 99.99% for a trio case (if the mother, child and alleged father were all tested) means that the tested man is the biological father.

Exclusion: A probability value of 0% means that the tested man is not the biological father.

The probability of paternity never reaches 100% because a paternity test is calculated against a population database. A 100% probability is only possible if every man in the world is tested. A probability value of 99.99% or higher eliminates most other men from being the biological father, virtually proving the paternity relationship between the child and the tested man.

Probability values below 99.99% for a standard paternity test (trio) are considered inconclusive; paternity tests that show this result require extended testing in order to have a definitive inclusion or exclusion result.

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How much does a paternity test cost?

The average price for a legal paternity test is $450 to $500, but there is a wide range in pricing. However, a properly conducted and accurate paternity test should not cost more than $550. The more rigorously controlled laboratories are likely to have higher internal costs that may subsequently be passed along to their clients. Naturally, it costs more to run a highly controlled, consistent testing laboratory than it does to perform inferior tests with poor processes and/or obsolete equipment.

Some state governmental agencies arrange for contracted rates with DNA testing laboratories, allowing them to offer paternity tests at rates well below the standard fee. Check with the court or another government agency with whom you are working to see if they can provide testing services at a reduced cost.

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What is the difference between private and legal paternity testing?

Private DNA testing is not legally admissible in court. Individuals collect all of the DNA samples themselves, and there is no way to confirm who gave the sample.

Legal DNA testing requires that all parties go to a designated collection site so that a Chain of Custody can be established. Chain of Custody is a process used to maintain and document the chronological history of the samples (who has control of the samples at what time). At the collection site, you will be asked to sign consent papers and to designate an address where you want the result sent. You will have to provide personal information, photo identification, and a thumbprint in order for the Chain of Custody to be accurately documented. No one can provide samples or take the test for you.

The chain of custody must be documented in order to be court-approved. Chain of Custody collections are performed if the paternity test result is to be used for legal purposes, such as claiming child support, Social Security, or inheritance benefits.

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What is a "motherless"paternity test?

A motherless paternity test can be done if the mother is unable or unwilling to participate in the testing process. This test will provide the same conclusive results as a standard paternity test.

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Is it true that 1 in every 3 men tested are not the father?

Several organizations have reported that 1 in every 3 men tested for paternity are excluded as the father, but the importance of the exclusion rate has been exaggerated because the statistics have been misinterpreted in the past. The suggestion that 30% of men are misled into believing they are biological fathers of children is not correct.

The rate of exclusion includes many different issues. It is important to remember that the tested men are alleged to be fathers. A woman may declare more than 1 man as a possible father because she was sexually active with more than 1 man. These men were not deceived into believing they were fathers and then later discovered they were not. Paternity tests simply sort out which man is the biological father. Another factor to keep in mind is that some men are accused and tested because a man who is not excluded alleges that the mother had multiple sexual partners as part of his defense. There are also occasions where a man is required to be tested because of a legal presumption. For example, if a mother properly names the correct father, but she is (was) married to someone else, there is a legal presumption that the husband is the father. The husband is then tested to rebut the legal presumption, not because he was misled into believing he is the biological father of the child.

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How do I find more information about DNA testing on the Internet?

If you have not done so already, you can search the Internet using search engines such as Google, Yahoo, and MSN. Use keywords relating to the type of testing you would like. For instance, if you want to find information about paternity tests, type "paternity testing." If you want to find out more about other types of DNA testing, type "DNA testing." If you know the specific type of test that you want, you can also search for that test by name. For instance, if you are a grandparent who wants to ensure your grandchild is actually your son's child, type "grandparentage testing."

You can also check our online Resource Links.

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Click on the logos below to visit DNA company websites.
Go to DNA Diagnostics Center DNA Diagnostics Center is the largest privately owned DNA testing company in the U.S.
Below are Private (in-home collection) DNA Testing Companies, click logos to link.
Go to American Paternity American Paternity specializes in comprehensive testing, paying special attention to customer service.
Go to Beta Genetics Beta Paternity specializes in in-home DNA testing, and they are the largest provider in North America.
Go to DNA Roots DNA Roots specializes in DNA testing for adult children.
Go to Gene Match GeneMatch specializes in infidelity testing.
Go to GeneSys GeneSys specializes in relationship testing and provides DNA banking.
Go to Prophase Genetics Prophase Genetics specializes in private paternity testing.
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