DNA, the genetic blueprint, is composed of a string of 3 billion
individual units called nucleic acids, of which there are four kinds.
The exact order of these units, called the sequence, is unique
to all individuals except identical twins.
DNA is subdivided into 23 paired structures called chromosomes.
One of each pair of the child's chromosomes is
derived from the mother and one from the father.
DNA is the same from cell to cell in any given person,
and is passed from parent to child according
to the principles of Mendelian genetics, whereby one of each pair
of chromosomes passes from parent to child in an independent fashion.
In the laboratory, at least 11 different paired regions of DNA,
are individually examined from the
mother, child, and putative father.
These regions have been carefully chosen because they show
great variability in size (number of units) from person to person.
Thus the sequence inherited by a child from its' mother
usually differs from that from its' father
in each of these variable regions.
Testing delineates which half of the child's DNA derives from the
mother, and the other half is examined to see if it matches
that of the putative father.
All testing includes a sex test to serve as further identification.
Exclusion from paternity is indicated when the child's DNA
does not match that of the mother or putative father
in a minimum of two regions.
The probability that a falsely accused man
will be excluded as the genetic father of a particular child
ranges from greater than 99 to greater than 99.99 per cent.
If the analysis does not exclude the accused man,
that does not necessarily indicate that he IS the genetic father.
His genetic makeup may be identical to that of
another man in the general population,
who may be the genetic father.
In this case, Serotech will compute the statistical
probability that the accused is the true
genetic father of the child.
This statement of probability is based on the frequencies
of the regional chromosomal sequences studied
(as described above) in large, randomly selected
populations of a given race.
The Laboratory will calculate how many other men
in the population possess the combination of
regional chromosomal sequences of the specific DNA marker
regions paternally inherited by the child, and express
the result as a percentage that indicates the probability of paternity
of the accused man compared to that by a group of randomly
chosen men in the population.