PATERNITY TESTING THRU GENETIC MARKERS
DNA tests provide evidence regarding the alleged family relationship. It does this thru DNA genetic markers.
This is a brief explanation of the meaning of the numbers and other items that appear in a DNA test report. This is a sample report and shows Sixteen sites as being tested. Some labs will use more or less than sixteen. Be sure to ask your lab provider how many sites are tested.
The laboratory tests the DNA isolated from buccal (cheek) swabs to locate certain regions of chromosomes that vary in length between individuals. Sixteen of these sites are tested. Each site is called a “locus”, (“loci” – plural). Analysis of these 16 loci in a large population has revealed many different sized fragments, or alleles, associated with each locus. These are the genetic markers used in parentage analysis.
Because each individual has two of each type of chromosome, one inherited from each parent; everyone has two alleles at each locus. These two alleles are sometimes identical (homozygous), but usually they are not the same size (heterozygous). During parentage testing, the laboratory identifies the length of the two alleles found at each locus.
The columns marked “allele” on the report contain numbers indicating the two alleles found at each locus (or one number if they are the same size).
If, for example, a child has two alleles that are designated 12.1 and 18, and if the mother has alleles 12.1 and 16, then the child inherited the 12.1 allele from the mother. The child has to have inherited the 18 allele from the father. The 18 allele is the “obligate paternal allele.” Generally, the alleged father must have this allele if he is the biological father of the child.
Fifteen different loci are used as genetic markers in the tests, as well as one (Amelogenin) to confirm the sex of the person providing the sample. If the alleged father does not have the matching allele at every tested locus, then he usually cannot be the biological parent. If he does have it, then he could be the father.
