DNA Fingerprinting | Genetics | Biology | FuseSchool

[Music] what is dna fingerprinting or dna profiling leicester university geneticist alec jeffries developed a technique called dna fingerprinting in 1985 it allows dna samples from different people to be compared to look for similarities and differences it's used for solving crimes and can also confirm if people are related to each other like in paternity testing any two people in the world have 99.9 percent of their dna the same so this process analyzes the differences in the remaining 0.1 percent this modern technology is called dna profiling it's a very sensitive technique which only needs a few skin

cells a hair root or a tiny amount of blood or saliva there are sections or loki of chromosomes where instead of a gene consisting of a long sequence of bases there are much shorter sequences of three four or five bases that are repeated many times for example these repeated sequences are called short tandem repeats or str at these places on the chromosomes where we find these strs there are areas that vary in number of repeats dna profiling only looks at these strs a cell sample is collected this could be from some blood at a crime

scene or a swab from the inside of someone's cheek for example the dna is then extracted from the sample many copies of this dna may be made using the polymerase chain reaction or pcr special enzymes called restriction endonucleases are used to cut the dna up into different sized pieces the dna samples are then put into wells in a special gel called agarose for the process of gel electrophoresis which separates the dna fragments by size the pattern is then transferred to a nylon sheet in southern blotting and finally the lines produced by the dna samples from

different people are compared so let's have a go at using dna profiles to solve some mysteries an item was stolen in a burglary a drop of blood was left behind by the thief samples of dna were taken from four suspects and compared to the sample left at the crime scene which suspect is guilty here's a clue look for the one that is most similar to the one from the crime scene pause the video while you decide suspect 3 is guilty can you see how the pattern of bands matches in suspect 3 and the crime scene

their dna is the same let's try another a soldier has been killed in an explosion and has lost his dog tags that identify him three soldiers are missing from their unit so the army asks the three sets of parents for a dna sample so they might compare it to the soldier's dna and therefore make an identification remember the soldier will only share half of his dna with each parent so which set of parents is the soldier the son of pause the video while you decide parent c and d as you can see he inherited the

first band from parent d and the second third and fourth from parent c and so on so now you understand how dna profiles or fingerprints are made and seen some examples of where they can be used you can even interpret a dna profile please like and share our videos with your friends if you have any questions that you want help with just comment below