DNA Profiling Essay Sample

DNA profiling is extensively used in forensic science to identify individuals, criminals in particular, to samples of human tissue or fluids found at crime scenes. All humans will have a majority of their DNA material in common, and DNA profiling is what's used to separate the portions of DNA that's particular to an individual.

Electrophoresis
Electrophoresis, in general, is the migration of the charged particle under the influence of an electric field. During the context of DNA forensics, electrophoresis is the method of separating and sorting DNA fragments, by passing an electric current via a block of gel (usually polyacrylamide, which has a high resolving power) containing said DNA fragments at a single end, thus generating a DNA profile.
DNA strands are broken into these fragments by introduction of a restriction enzyme, which creates one cut on each with the 2 phosphate backbones with the DNA double helix, on portions in the helix that contain a “recognition sequence,” a certain nucleotide sequence that the restriction enzyme reacts to. (Restriction Enzyme, 2006)
The polyacrylamide gel, which is probably the most usually applied in true practice, is really a cross-linked polymer of acrylamide, a powerful neurotoxin (polyacrylamide itself is non toxic). It's a network of polymer chains, similar to a (compressed) sponge, through which the DNA fragments will migrate. (Polyacrylamide, 2002)
Electrophoresis depends on this house from the gel to separate the DNA fragments into groups—the little fragments will migrate faster, whilst the larger fragments will “catch” over a network of polymer chains and will thus migrate slower. The fragments thus grow to be grouped according to size, and also a DNA profile is obtained (Polyacrylamide, 2002). This system is critical since the grouping and location of these bands over a gel is distinct towards person (from which the DNA came from) and can also be employed to identify an individual.
After the electrophoresis is completed, a dye for example methylene blue is used to visualize the bands. (Gel Electrophoresis, 2006)

PCR
In some cases, electrophoresis might not be right away possible due to a extremely limited DNA sample; in these kinds of cases polymerase chain reaction (PCR) will likely be useful. PCR is really a molecular biological process which could duplicate particular regions of DNA with accuracy, normally within a few hours. This can be exciting in cases where only a small sample of DNA was obtained and there's a must develop a DNA profile.
To use PCR to duplicate DNA, the DNA sequences at each ends of a strand ought to be known. The DNA is duplicated in a thermocycler inside presence from the Thermus aquaticus (Taq) polymerase and sequence-specific primers of DNA. (Slish)
The program starts using a gene or segment of DNA, that may be denatured (its strands separated) at 94°C. The temperature is then lowered to 45-55°C, at which the primers, complementary towards the freed ends on the DNA strands, anneal, or attach themselves to their complementary sequence on the DNA strands, serving as catalysts for duplication in the original DNA double helix. Once annealed, DNA polymerase extends the primers at 72°C, copying the sequence of the strand. This effects in doubling from the quantity of DNA per cycle, which takes about a couple of minutes each. (Polymerase Chain Reaction, 2006)
The thermocycler repeatedly raises and lowers the temperature, which causes the DNA molecules to copy themselves. Inside a short time, thousands of copies in the target sequence are produced. (Rabinow, 1998)

Difficulties in PCR
Some problems of PCR are: the reaction is extremely sensitive to divalvent cations and nucleotides; proper primer type is of utmost value for effect amplification—the primers need to be quite specific; feasible reactivity with non-target DNA sequences; primers must not be able to anneal to themselves or each other; the size of DNA molecules to be amplified is limited; polymerase errors—the Taq polymerase can make mismatches when incorporating new bases into a strand; and even very smaller contaminations of unwanted DNA can ruin the results. (Slish)

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