Denton Family Attorney

Paternity Testing

A paternity test is a scientific test to determine if a man is the biological father of a child. In some child support cases, such a test may be required to prove whether a man has a paternal obligation to support a child. Laws regarding paternity tests vary by jurisdiction. Some, for example, require the consent of the mother or the directive of a court of law. Others may also limit the amount of time that a putative father has to challenge his status. Such stringent requirements have, in the eyes of critics, facilitated a type of crime known as paternity fraud, in which a woman falsely claims that a man is the biological father of her child, usually for the purposes of claiming child support payments or similar financial benefits.

The concept of paternity testing is not new, but has progressed with the advancement of technology.

ABO Blood Type Test

The ABO blood type test is based on the way that blood type is genetically passed from generation to generation. An adult human possesses two ABO blood type alleles, or genetic factors, which interact to determine blood type. For example, an adult with an A-type allele and a B-type allele would have an AB blood type. The O-type allele is said to be recessive, meaning that it will be ‘overwritten’ if it interacts with either an A- or B-type allele. Therefore, a person with an A-type allele and a O-type allele will have a genotype, or genetic ‘profile’ of AO, but a phenotype, or actually expressed blood type, of A.

An older method of establishing paternity, the ABO blood type test is probably more useful in disproving paternity than confirming it. This is because of the rules governing the genetic inheritance of blood type. The situation can be thought of as a sort of triangle – if the blood types of two parties (either the two parents, or one parent and the child) are known, the range of possible blood types for the remaining party can be determined. If there is a mismatch between the possible blood types and the actual blood type of the person, then blood relation is impossible. For example, it is impossible for two parents with A-type blood (meaning either genotype AA or AO) to give birth to a child with B-type blood, because neither parent possesses a B-type allele to pass on.

DNA Testing

Modern paternity testing is usually done through DNA fingerprinting. Deoxyribonucleic acid is the material which contains most of the genetic data for the human body. Every person has a unique DNA sequence which can be used for identification. By comparing key portions of the DNA sequences of two people, it is possible to determine if one could possibly be the parent of the other.

There are two main methods of DNA fingerprinting commonly used in paternity tests: the restriction fragment length polymorphism (RFLP) test and the polymerase chain reaction (PCR) test.

The RFLP test cuts a DNA strand into specific fragments using restriction enzymes. These fragments are then sorted by size by running them through a special gel with an electrical charge at one end. Because longer fragments have a more difficult time traveling through the gel, they will not travel as far as the shorter fragments. By comparing the resulting pattern, the genetic relationship between two individuals can be determined.

The PCR test uses a DNA polymerase to essentially replicate a section of DNA multiple times, creating an ‘amplified’ section of DNA which can be analyzed. By selectively limiting which sections of DNA are amplified, scientists can create genetic fingerprints for an individual.

If you are involved in a child support or child custody battle, a Denton child custody lawyer can help you argue your case. Call Alexander & Associates today at 972-420-6560.