Facts: How DNA testing works | Find out Here

wigo NG ...733 days ago
DNA testing is also called DNA typing , DNA profiling, genetic fingerprinting , genotyping , or identity testing .The procedure involves isolating and identifying variable elements within the base - pair sequence of DNA ( deoxyribonucleic acid).
Forensic DNA analysis ( usually analysis of short tandem repeats (STRs )) uses the polymerase chain reaction ( PCR ), gel electrophoresis , and detection .
This is how crime and accident scenes DNA evidences are used for detecting criminals , identifying missing persons , identifying corpses, for post - conviction testing , for repealing wrongful convictions , and for clarifying familial ties and disputes .

A fetish Nigerian restaurant was caught serving human meat . Some big business scammers were found adding horsemeat to their “ beef” products. These are cases where DNA testing is useful . DNA testing is also used for food testing , fordesigning drought- resistant plants , and for producing biological drugs from genetically altered bacteria.

To prepare for PCR , DNA is isolated from a sample in a multi - step process that may be done manually or with an instrument such as the COBAS ® AmpliPrep Instrument . PCR takes place in a bench - top equipment called a thermocycler and involves thefollowing steps .
 Denaturing : during this process the temperature is increased to separate the strands .

 Annealing : during this process the temperature is decreasedto allowprimerstopairtocomplementary DNA templates. (Primers determine the DNA sequence to be amplified .)
 Extension : during this process the enzyme called polymerase extends the primer to form new DNA strands .

 Exponential amplification : the cycle is repeated and existing DNA strands are copied to form new DNA strands .
The varied length strands are then separated by gel electrophoresis.
Gel electrophoresisis a process that is used to separate proteins and nucleic acids that differ in size.

In the process of DNA testing , DNA fragments cut by restriction enzymes are separated based on their rate of movement through a porous gel in an electric field . The prepared DNA samples are loaded into small wells at one end of the gel from where they travel towards the other end of the gel. The gel is immersed in a buffer solution within a chamber between two electric nodes . An electric current is applied and compels thenegatively charged DNA fragment to move towards the positively charged end of the gel . The distancealong the gel that a DNA molecule travels is inversely proportional to its length. The smaller strands travel faster to the other end of the gel by electrical attraction. The separated proteins appear as bands within the gel , each band representing a certain molecular size, but are invisible within the gel .

After the current is turned off , a dye is added to reveal the separated bandswhich are made to fluoresce in ultraviolet light or when passed through a laser .Somemethods of detection capture imprints of the separated bands on an X - ray film. Newer methods use DNA reads on a computer screenandcomputerprint - outs .

In industrial- type speedy automatic sequencing machines, a complex set of procedures is used to prepare DNA for sequencing. ” When DNA is finally in a form that the machines can read, it has been chopped up , copied , chemically modified , and tagged with fluorescent dyes corresponding to the four different DNA bases , or genetic letters .”
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