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The development of genetic engineering and the uses of dna profiling

Jeffrey at the University of Leicester while he was studying the gene for myoglobin. He found that myoglobin genes contain many segments that vary in size and composition and have no apparent function.

DISCOVERY OF THE DNA FINGERPRINT

Jeffrey called these segments minisatellites because they were small and surrounding the part of the gene. The minisatellites account for less than 1 percent of the total DNA of human. DNA Probes Jeffrey isolated several of these minisatellite genes and inserted one of them into bacteria. Large amount of the DNA segments could then be produced and purified. What is DNA Fingerprinting used for At present, DNA fingerprinting is the most powerful and authoritative method to identify an individual due to the different polymorphisms.

With the exception of identical twins, the genetic make-up of every human being is different from one another. There are two types of DNA structural polymorphisms: Site polymorphism - change of one or more nucleotides at a particular site 2.

Length polymorphism - number of repeating units is different at a particular locus.

  • After DNA extraction, restriction enzymes are added, which work like scissors to cut the DNA into the smaller segments that are different between individuals;
  • The DNA is thus separated into different bands with fragments in each one progressively getting smaller in size.

Isoloation of DNA a. DNA samples are obtained from substances such as blood, semen, hair roots, or saliva.

ADDITIONAL MEDIA

The individual cells from the sample are split open, and the DNA is separated from the rest of the cellular debris. Cutting with restriction enzyme a. The DNA is then treated with restriction enzymes which cleave the DNA into smaller fragments by cutting at specific sites.

The result is a unique collection of different-sized fragments. Since the minisatellites from any two individuals have different compositions, they are cleaved at different sites, producing fragments of different lengths.

These different lengths of fragments existing between individuals are called as restriction fragment length polymorphisms RFLPs a.

The DNA fragments are then applied to one end of a thin, jellylike substance called an agarose gel. An electric current is passed through the gel for a short period of time. The negatively charged DNA fragments will migrate across the surface of the gel in response to the current. The smaller and more mobile pieces of fragments will travel farther.

  • However, one of the sons went back to Ghana and was stopped from returning to the UK because he had a forged passport;
  • There are two types of DNA structural polymorphisms;
  • Pitchfork was apprehended and his blood tested; the long-sought DNA match was made, and Pitchfork was convicted of both murders;
  • Moreover, the testing confirmed that all four children had the same father 7;
  • Each individual has a signature fingerprint 5.

The DNA is thus separated into different bands with fragments in each one progressively getting smaller in size. Because the gel cannot be easily handled, a thin nylon membrane is laid over its surface and covered by layers of paper towels.

As the towels draw moisture from gel, the DNA is transferred onto the surface of the nylon membrane. This process is called blotting. Soak the nylon membrane overnight. The DNA bands are still invisible to the eye, and there are too many to be useful.

Therefore, a solution of the radioactive probes made from minisatellites is washed over the surface of the membrane. If any of the probes have the same compositions as a part of a DNA fragment, they will bind together. The probes will ignore the vast majority of the hundreds of bands present.

  1. Jeffrey called these segments minisatellites because they were small and surrounding the part of the gene. The minisatellites account for less than 1 percent of the total DNA of human.
  2. The pattern of DNA segments, composed of perhaps 15 to 20 bands, was different for each one.
  3. First, the DNA is extracted from the specimen i. Because the gel cannot be easily handled, a thin nylon membrane is laid over its surface and covered by layers of paper towels.
  4. The smaller and more mobile pieces of fragments will travel farther.
  5. The DNA is thus separated into different bands with fragments in each one progressively getting smaller in size. Separate the amplification products according to the size by electrophoresis 4.

To see the pattern of bands, place a sheet of photographic film on top of the membrane. The radioactive labels will expose the film and ultimately produce a pattern of thick and thin dark bands.

Discovery, development, and current applications of DNA identity testing

This pattern of bars is the DNA fingerprints. Copy a specific fragment many times amplification using the polymerase chain reaction PCR 3. Separate the amplification products according to the size by electrophoresis 4. Compare the size pattern of the amplification products 5. The pattern obtained may vary between individuals because of the length polymorphism Applications of DNA Fingerprinting.

  • Refining the assay After the success of that case, Professor Jeffreys was bombarded with many inquiries;
  • There are two types of DNA structural polymorphisms;
  • Other uses include confirming a diagnosis of hydatidiform mole and resolving issues of specimen identity in cases of specimen mislabeling or misidentification;
  • Other clinical applications are based upon the methods developed for forensic testing;
  • The radioactive labels will expose the film and ultimately produce a pattern of thick and thin dark bands;
  • Later, new markers for identity and paternity identification were based on variations of serum proteins and red blood cell enzymes; eventually the human leukocyte antigen system was used 2.