DNA ANALYSIS
DNA analysis is the name given to the interpretation of genetic sequences, and it is used for various purposes such as to differentiate or to identify species or individuals. The materials used in carrying out DNA analysis include cells, blood, semen, tissue, faeces, saliva, hair, urine and bones. Investigators usually collect items that may have come into contact with a person or a specie. Such items may include tools, clothing, masks or gloves. Various steps need to be followed when carrying out DNA analysis.
Biology
After the collection of material from a crime scene or an individual, the DNA is extracted from the biological sources material and put on measurement to see the quantity of the DNA that has been collected. After the DNA has been separated from its cells, some special regions get to be copied by use of Polymerase chain reaction (PCR). PCR is capable of producing many copies of a DNA segment.
Technology
The PCR products are later detected and separated to analyze the STR region being examined. The commonly used separation methods include capillary electrophoresis and slab gel. Fluorescence detection has proved to be of great importance when measuring PCR-amplified STR alleles. After STR alleles have been detected, sample genotyping is used in determining the number of repeats in a DNA sequence. Various laboratories have their methods of DNA typing.
Genetics
The DNA profile of a sample is compared with other samples. In the case of forensic investigations, these samples are made to connect with other reference samples of a known suspect who might have committed a crime. If there is no connection between the known sample and the questioned sample, then the sample is thought to have originated from other sources. When DNA analysis fails to match the term mostly used is exclusion. However, when the DNA analysis matches with a specific individual or specie, the term used is inclusion.
After DNA has been carried out, test results are usually generated. The results usually include the match probability with the match in question.
Types of DNA Analysis
There are various methods used to analyses DNA samples
Restriction Fragment Length Polymorphism
Restriction Fragment Length Polymorphism (RFLP)
It happens to be the old method of analysing DNA samples. It produces white and black images and mainly involves cutting down the DNA and targeting a specific sequence. The sequences are later cut into different strands of different lengths. This brings out white and black genetic fingerprints with the shortest strand at one end and the longest strand at the other end. This kind of method requires a sample that is free and not contaminated.
Short Tandem Repeat (STR) Analysis
STRs are DNA sections ranging between one to five nucleotides which are repeated in a DNA sequence severally. Compared with RFLP, STR analysis can be carried out with samples which are of lower quality. This method involves checking the many times STR sequences get to be repeated. This kind of method is mostly used to disapprove or to prove biological relationships.
Single Nucleotide Polymorphism (SNP) Analysis
SNPs are further referred to as genetic variants and are segments in a DNA where nucleotides differences are present in individuals. In this case, a DNA sample is usually run through a computer chip. The chips are designed to detect about a million SNPs in a DNA sample.
Y DNA Analysis
Y DNA analysis is used to trace genetic connections, and it is mostly used to solve sexual assaults in cases where some male suspects have been involved.
Mitochondrial DNA analysis
Just like the Y DNA analysis, mitochondrial DNA analysis aims at checking on genetic information which is mostly inherited from mothers. It is mostly used to check on the deep maternal ancestry. Even though DNA is mostly found on nuclei of cells, Mitochondrial DNA is usually carried out on the mitochondria structures of cells.
In recent years DNA analysis is being used as a powerful criminal justice tool. DNA analysis can be used to identify criminals because of the presence of biological evidence accurately. On the other had DNA samples can be used to free some suspects who have been accused falsely of having committed crimes. DNA analysis is becoming an essential tool in ensuring fairness and accuracy in criminal justice systems. Before DNA analysis came into being, solving issues related to a crime was difficult because investigators had to depend on fingerprints which were being obtained in crime scenes. Criminals would ensure that their fingerprints are never left on crime scenes by ensuring that they ware gloves or wiping surfaces. DNA samples can be collected from almost all surfaces. Most criminals do not leave biological substances such as earwax, hair, sweat, saliva, mucus or skin.
Apart from being used to solve criminal cases, DNA analysis is used to solve paternity issues, ancestry and identification issues. In recent years DNA has been of much help in solving complicated issues which have remained unsolved for many years. Before the advancement in techniques used for DNA analysis, there was a need for large quantities of uncontaminated materials. However, recent methods can be used to produce DNA results where there are low-quality samples. Techniques have been improved such that DNA can be extracted from contaminated sources while it has also become faster and cheaper to get DNA results. However, the interpretation of DNA analysis mainly depends on experts.