On a DNA test, why are the results are always read 99 point whatever and not 100 percent?

Answer 1

Research in DNA sampling shows that there is a billion-in-one chance that the DNA of two unrelated individuals will match. This is a good enough ratio, combined with the fact that even though there are more than 6 billion people inhabiting this planet, two people will not have the same DNA due to geographical diversities, etc. However, the still cannot be said that there is a hundred percent chance that a given sample is unique to an individual. Hence, the DNA match output is always printed as a probability ratio, and you get a probability of 99 point something, and not a 100%.

Answer 2

Because only identical twins have identical DNA, and there is even some question about that.

The chance that two unrelated people have identical DNA is therefore zero, so a match of 99+% between a test and a suspect is far better proof of guilt than a thousand eyewitnesses (strictly speaking, it should be 100% if it were the same person, but no test is ever perfect).

Answer 3

A DNA test uses a limited number of polymorphic (showing differences in the general population) markers. The test establishes the likelihood that two samples are identical due to chance rather than being from the same individual. With the number of markers currently used the probability is typically 99.99% likelihood of a match not being by chance (or one in ten thousand likelihood of matching by chance). Using more markers would allow this to be even more precise but this is already "beyond reasonable doubt" ie the legal standard.

Answer 4

There is a VERY small chance that two people could have the same DNA

Answer 5

It's called "Covering Your ***".

Answer 6

its just simple.DNA test is not perfect...