dna fingerprinting

a picture of DNA fingerprinting

DNA. It's what makes you unique. It's the stuff that tells each and every one of your body's 10 trillion cells what it's supposed to be and what it's supposed to do. And although your DNA is different from that of every other person in the world—unless you have an identical twin—it's the same in every cell that makes up your body. That DNA is unique from person to person but the same from cell to cell in one person can be a handy thing, especially when it comes to DNA fingerprinting. DNA fingerprints can be used for anything from determining a biological mother or father to identifying the suspect of a crime. And, as may someday prove to be the case with Sam Sheppard, it can be used to clear someone's name. But what exactly is a DNA fingerprint? Well, it certainly isn't an inky impression of a DNA strand. Compared to unimaginably small DNA, a fingerprint is HUGE. So what is it that we're looking at, and how is one of these fingerprints made?

DNA fingerprinting is a term that has been bandied about in the popular media for about fifteen years, largely due to its power to condemn and save, but what does it involve? In short, it is a technique for determining the likelihood that genetic material came from a particular individual or group. 99% of human DNA is identical between individuals, but the 1% that differs enables scientists to distinguish identity.

The DNA alphabet is made up of four building blocks – A, C, T and G, called base pairs, which are linked together in long chains to spell out the genetic words, or genes, which tell our cells what to do. The order in which these 4 DNA letters are used determines the meaning (function) of the words, or genes, that they spell.

But not all of our DNA contains useful information; in fact a large amount is said to be “non-coding” or “junk” DNA which is not translated into useful proteins. Changes often crop up within these regions of junk DNA because they make no contribution to the health or survival of the organism. But compare the situation if a change occurs within an essential gene, preventing it from working properly; the organism will be strongly disadvantaged and probably not survive, effectively removing that altered gene from the population.

For this reason, random variations crop up in the non-coding (junk) DNA sequences as often as once in every 200 DNA letters. DNA fingerprinting takes advantage of these changes and creates a visible pattern of the differences to assess similarity.

Stretches of DNA can be separated from each other by cutting them up at these points of differences or by amplifying the highly variable pieces. ‘Bands’ of DNA are generated; the number of bands and their sizes give a unique profile of the DNA from whence it derived. The more genetic similarity between a person, the more similar the banding patterns will be, and the higher the probability that they are identical.

THIS IS MY BLOG ON DNA FINGERPRINTING