Heritage Album

How accurate and reliable are DNA and paternity tests?

I often hear the figure "99.9% plus" quoted but over the years I've learnt to be cautious of claims that aren't decisively backed by peer-reviewed scientific testing; lie-detector/polygraph machines are a good example of scientific evidence being absent despite popular belief. I live in an area where there are literally dozens of people who look so much like me it's creepy; they are obviously distant cousins from somewhere on the family tree and there are a lot of them living in the same town. I've noticed the same trend all over the Country; people from the same district often have similar features. Could this foul DNA profiling? Saying that a person is a "1 in 10 million match" sounds pretty certain but what if the other 60 or so people who are also a match live in the same location? There also seem to be a rising number of screw-ups in laboratories. http://www.washingtonpost.com/wp-dyn/content/article/2005/08/20/AR2005082000998.html

Public Comments

1. It has to be done specifically, using DNA fingerprinting, it is easy to make a mistake. It also helps to have the DNA of the person involved (e.g. blood, semen, saliva, hair). It isn't 99.9%, in fact it is around 96%. It is an expensive process, and takes quite a while. I have a test on this tomorrow. They may look like you, but they don't have nearly anything similar to your DNA. Everyone has their own unique DNA which codes for everything in your body. The only people that have the same DNA/genetics are identical twins. So, I wouldn't worry about it coming up the same unless you have an INDENTICAL twin. These are the steps, just to aid my revision: 1. DNA sample is extracted/isolated 2. A restriction enzyme is used to split it up specifically (everyone's will be split in different places because it is specific, and everyone is unique) 3. It is then put onto an agar plate (electrophoresis) where it is charged. DNA is negatively charged, so it moves towards the positive anode 4. The smaller pieces of DNA will move further towards the anode 5. The DNA is marked by a radioactive marker, and put under an Xray, type machine (kindof like chromotography) 6. The machine picks up the DNA and VIOLA!! You can only mess it up if it isn't done correctly.
2. DNA tests are about 99.9% accurate. The results are completely accurate themselves, but you have to consider human error. Lab errors can occur, or the DNA sample itself may not have an extensive amount of DNA to test. These "distant cousins" can be traced to you through DNA. You have the same Y chromosome as your father, his father, his father, etc. That includes the brothers as this DNA is passed from father to son. This means that you would match with anyone sharing this Y DNA. This goes the same for the maternal side. Mitochondrial DNA is passed from your mother, from her mother, etc. These relations can be tested.