DNA Inheritance

Think of DNA as the instruction manual for how you are made; it is responsible for the transmission of characteristics you inherit from your parents. Every individual is made from cells containing DNA in the cell nuclei. DNA is comprised of 23 pairs of chromosomes (46 chromosomes in all), and each of these contains genetic sequences. We inherit half of our chromosomes from our mother and half from our father.

DNA is your genetic “fingerprint.” No two people in the world have the same DNA, except for identical twins. Your DNA sequence is what we examine to determine paternity or maternity. We initially study up to 16 different loci (locations) on each person’s DNA. Since every individual has 2 copies of each chromosome (1 from their mother, 1 from their father), they will have two readings for each locus tested. Once testing is complete, DNA loci are compared. Readings for each tested individual will have two numbers. For example, in paternity testing, 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.

If there are 1 or 2 non-matches, the samples are examined further to obtain conclusive results (additional testing of up to 25 total markers). If there are 3 or more non-matches, it is concluded that the tested man cannot be the biological father of the tested child. The probability of paternity is 0%.

For mtDNA testing, scientists are specifically looking for inherited variations of the genetic code in the mitochondrial DNA. These variations are typically passed down from mother to child without changing. This means that a person can trace their lineage through their maternal side, often beyond their parents' generation in their family tree.