DNA is material that governs inheritance of eye color, hair color, stature, bone density, and many other human and animal traits. DNA is a long but narrow string-like object. A one foot long string or strand of DNA is normally packed into a space roughly equal to a cube 1 millionth of an inch on a side. This is possible only because DNA is a very thin string. With this DNA, DNA paternity testing services can match with pinpoint accuracy the biological mother and father with their offspring.
A strand of DNA is made up of tiny building blocks. There are only four different basic building blocks. Scientists usually refer to these using four letters: A, T, G, and C (which stand for the substances adenine, thymine, guanine, and cytosine). Another way of referring to the building blocks or letters is to call them bases. The sequence of bases can code for properties of the body's cells. The cells can read this code. Some DNA sequences encode important information for the cell. Such DNA is called "coding DNA." Our cells also contain much DNA that doesn't encode anything that we know about. This type of DNA is called non-coding DNA or "junk DNA."
DNA evidence uses a special kind of length polymorphism found in non-coding regions. These special variations come from stretches of short, identical repeat sequences of DNA. A particular sequence can be repeated anywhere from one to thirty times in a row, and so these regions are called variable number tandem repeats (VNTRs). The size of a DNA fragment will be longer or shorter, depending on how many copies of a VNTR there are. For DNA paternity testing services, the great thing is that the number of tandem repeats at specific places (called loci) on your chromosomes varies between individuals. For any given VNTR loci in your DNA, you will have a certain number of repeats. You inherit one copy of each chromosome from your mother and father.
There are two ways DNA testing services analyze DNA: Restriction Fragment Length Polymorphism (RFLP) analysis and Polymerase Chain Reaction (PCR) analysis. The steps that DNA paternity testing services take in RFLP analysis are:
- Isolate the DNA
- Cut the DNA up into shorter fragments containing known VNTR areas
- Sort the DNA fragments by size
- Compare the DNA fragments in different areas
The way DNA testing services are able to sort tiny DNA fragments by size is by using gel electrophoresis. After the DNA fragments are sorted, they look at the results using a Southern Blot. RFLP analysis requires large amounts of relatively high-quality DNA. Getting sufficient DNA for analysis has become much easier since it became possible to reliably amplify small samples using the polymerase chain reaction (PCR). With PCR, tiny amounts of a specific DNA sequence can be copied exponentially within hours.
The information provided by this technology is useful for legal purposes, and for some personal situations. It is over 99% accurate, and is today relatively inexpensive (paternity can be established for a couple of hundred dollars). If you need the aid of DNA paternity testing services for whatever reason, search online and you will find many options. Keep in mind that if the testing is for legal purposes you may have to have the test administered by a professional rather than obtaining an at home test and doing it yourself.
By Greg Hitchcock