When a DNA test is perfomed?

Question

Is only a small amount of the dna strand compared?

Answer 1

Hi. I love the way you ask this.

I can tell from your question you don't know a lot about DNA.

No problem.

That's why you asked the question. Right? And I'm so glad you did, because this isn't easy stuff to understand, but in legal situations it can be crucial.

In reality, there are 48 strands of DNA to compare. That's because there are 24 chromosomes.

Think of 48 socks (strands), each with a matching pair. Although they are pairs, they are not identical.

When DNA testing is performed, the strands being "interrogated" are chosen to show valid identity. And, although a lot of human DNA is identical from person to person, there are certain regions which truly show individualistic "differences".

So when testing is performed to highlight "differences", these DNA regions are the ones most often analyzed; the ones that are typically different (person to person) 99.9% of the time.

The amount of DNA used is becoming more and more insignificant as technology improves. Very tiny amounts can be amplified, so an abundance will be available for testing. That is hardly a factor these days.

What does seem to be a factor is the quality of the DNA molecule. It does have a potential to degrade. And when it degrades, it makes it much more difficult to analyze.

Take home points: Yes, people are 99.9% alike in DNA. But the .01% regions of DNA they are different, tend to be VERY different (99.9% of the time). This is where paternity testing and forensics testing achieve their great power.

DNA quantities (little or small), is not a huge impact on DNA testing anymore.

DNA quality is essential.

The personnel handling and testing the DNA is also a gigantic factor. If some boob is doing it, then things can easily go to SNAFU!

This process needs to be handled by qualified, registered, professionals! Always ask for credentials for the people doing the work!

The MD interprets the work. He doesn't perform the work. The boob who makes the mistake is likely the one who handles the DNA.

But, in all honesty, any mistake to be made is usually detected by the MD, and is corrected before the results are reported.

What I mean is the results are pretty accurate.

Best,

Answer 2

Most DNA testing, whether for criminal cases or for determining relationships, looks at a relatively small number of sequences that are scattered throughout the DNA (By the way dumbdumb, there are 23 pairs of chromosomes, not 24).
While the details of how this works are fairly complex, imagine your DNA as being a particular edition of a large book and each person has a different edition. If I look at the 3rd paragraph of page 78, many people will have the same, some will be different. If I look at another paragraph, again, some will be alike, some will differ. If I do this often enough I will find that everyone differs from everyone else somewhere in their book. In real DNA testing there are certain areas that are known to differ quite often, so they concentrate on looking at those.

Answer 3

In Biology AP, we put a strand of DNA through an electrophoresis machine, and we used a full strand of DNA, but stained certain parts of the DNA so only they would show up, giving us a picture of who the match is.

Answer 4

Depends on the DNA test. The most common types of forensic tests such as DNA fingerprinting are considered to be "multi-locus" meaning they compare many locations on the tested DNA.