Dna Fingureprinting
DNA FINGERPRINTING
Background Reading - Nelson Biology and Campbell Biology Purpose - To understand the basics of DNA fingerprinting used in the Canadian courts for crime convictions and paternity suits. Introduction The process of DNA fingerprinting was developed by Professor Alec Jeffreys at Leicester University in 1984 as a form of genetic analysis. It was first used in the law courts of England in 1987 to convict a man in a rape case. It has now been used successfully in many crime and paternity cases in North America. A strand of DNA comprises many genes with intervening sequences found between the genes. The genes along a length of DNA do not join up neatly with each other. In between the genes which code for protein synthesis are regions of bases which form a nonsense code. These are called hypervariable regions because they vary dramatically from one person to another. No two people, except identical twins, share the same set of regions. In the hypervariable regions a simple sequence of ten to fifteen bases called a core sequence can be repeated over and over again. It is as if the base sequence is "stuttering" and in some places there are very long lengths where a base sequence is repeated hundreds of times. In 1984, Jeffreys made his breakthrough when he discovered that core sequences could be used as genetic markers for the hypervariable regions. Jeffreys isolated two core sequences of DNA and copied them many times in the laboratory to produce large quantities of markers which he labelled with radioactive chemicals. Now the genetic markers could be used as genetic probes. The probes can be attached to core sequences in a sample of DNA to find the position of hypervariable regions using photographic film to detect the radioactivity.
Figure I - A Photograph Of Dna Fingerprints Of Five Individuals (From Science and Technology in Society, The Association of Science Education, Hatfield, England.)
Molecular Genetics Unit
Part I - The Fingerprinting
Background Reading - Nelson Biology and Campbell Biology Purpose - To understand the basics of DNA fingerprinting used in the Canadian courts for crime convictions and paternity suits. Introduction The process of DNA fingerprinting was developed by Professor Alec Jeffreys at Leicester University in 1984 as a form of genetic analysis. It was first used in the law courts of England in 1987 to convict a man in a rape case. It has now been used successfully in many crime and paternity cases in North America. A strand of DNA comprises many genes with intervening sequences found between the genes. The genes along a length of DNA do not join up neatly with each other. In between the genes which code for protein synthesis are regions of bases which form a nonsense code. These are called hypervariable regions because they vary dramatically from one person to another. No two people, except identical twins, share the same set of regions. In the hypervariable regions a simple sequence of ten to fifteen bases called a core sequence can be repeated over and over again. It is as if the base sequence is "stuttering" and in some places there are very long lengths where a base sequence is repeated hundreds of times. In 1984, Jeffreys made his breakthrough when he discovered that core sequences could be used as genetic markers for the hypervariable regions. Jeffreys isolated two core sequences of DNA and copied them many times in the laboratory to produce large quantities of markers which he labelled with radioactive chemicals. Now the genetic markers could be used as genetic probes. The probes can be attached to core sequences in a sample of DNA to find the position of hypervariable regions using photographic film to detect the radioactivity.
Figure I - A Photograph Of Dna Fingerprints Of Five Individuals (From Science and Technology in Society, The Association of Science Education, Hatfield, England.)
Molecular Genetics Unit
Part I - The Fingerprinting