DNA, RNA, and Chromosomes

What is the biological basis for DNA fingerprinting?

British geneticist, Alec Jeffreys (1950–) formulated the method of DNA fingerprinting, also known as DNA typing or DNA profiling, based on the fact that unique genetic differences exist between individuals. Most DNA sequences are identical, but out of 100 base pairs (of DNA), two people will generally differ by one base pair. Since there are three billion base pairs in human DNA, one individual’s DNA will differ from another’s by three million base pairs. To examine an individual’s DNA fingerprint, the DNA sample is cut with a restriction endonuclease, and the fragments are separated by gel electrophoresis. The fragments are then transferred to a nylon membrane, where they are incubated in a solution containing a radioactive DNA probe that is complementary to specific polymorphic sequences.


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