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As you probably know, DNA makes up chromosomes. There are pieces of chromosomes, known as genes, that give people their individual traits. Eye color, height, skin color, etc, are to a large part determined by genes (via chromosomes, via DNA.)
You also know what a fingerprint is. Everyone's fingerprints are unique (at least as far as we know.) You can use a fingerprint to figure out who someone is because nobody else has it. All you need is a picture of patterns. In the olden days this was done by transferring the loops an swirls using ink and paper, but I think now it is generally a device that's closer to a copy machine.
Just like a fingerprint, no two people have the same DNA. Contrary to popular belief, even identical twins don't have identical DNA (though it's close, there are variations that come from how one lives life, environmental factors, and natural mutations.) DNA fingerprinting is the idea that we can use these variations to do a few useful things:
- identify paternity,
- provide evidence in criminal cases,
- identify people,
- determine a predisposition for diseases and such.
The term DNA "fingerprinting," though, is a bit misleading. Mapping a person's genetic makeup is expensive, time consuming, and difficult. The actual "map" in most cases compares or looks at very small bits of the total structure, unlike a real fingerprint.
- Can be used to help determine biological relationship, such as who a child's father is,
- Can be used to, beyond a reasonable doubt, prove a person was present during criminal activity,
- Can be used, to a degree, to determine the likely-hood that an individual will contract certain diseases or cancers,
- Can be used to identify dead bodies that can't be recognized in other ways,
- Is fairly conclusive.
- It's much better at proving familial relationships than specific ones. It would take more work if, say, two brothers were being accused of fathering the same child.
- DNA evidence can be compromised in criminal cases in a lot of ways, and the evidence only helps prove that an individual was present at a certain location, not exactly when or what they were up to while there (other than in the case of sexual assault, where the DNA is a bit more damning if it's found on the victim.)
- DNA fingerprinting is expensive and takes a lot of time. Therefore, it is not very useful for everyday identification purposes. Fingerprints are much better and easier to process/store.
- While it is pretty conclusive, it's not perfect. We accept it as accurate, though, because perhaps the chances of error are 1 in 40 billion. Other times, though, depending on the quality of the sample, it may be something like 1 in 4. For criminal purposes, that may not be enough.
In short, DNA fingerprinting is the process of mapping out the sequence of and presence of certain genes in people an animals. It's expensive and time consuming, but fairly accurate under the right conditions.
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