الفهرس 
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Abstract
Forensic genetics became an important part of forensic investigations. The most remarkable is the discovery of STR analysis by Prof. Alec Jeffrey in late 1980s. STR are DNA sequences that are short so less vulnerable to degradation and show high variability between people. This is what is called DNA fingerprints. There are other DNA analysis types as RFLP and SNP. Also genetic materials other than DNA which is called epigenetics have their applications in forensic analysis.
Analysis begins with detection and collection of the appropriate sample that is suspected to have genetic material. Samples must be one of the biological fluids like blood, semen, saliva and others. Several preliminary and confirmatory tests are used to identify the sample type. According to the detected sample method of collection and suitable container are determined. Sample is transported to the laboratory to be analyzed or stored with the recommended precautions.
To analyze DNA, first it should be extracted from the cell and purified from contaminants and other cell components. Several methods of extraction are available. They differ according to the used extractor either organic or inorganic, automated or manual procedure and if it involves a purification step or not. The second step is to amplify target DNA by PCR. As different sites are to be amplified for DNA profiling, multiplex PCR is used. After that detection of target DNA is achieved by electrophoresis either gel or capillary electrophoresis. Now capillary electrophoresis is the commonly used type because it’s easier, faster and automated. Electrophoresis and detection of DNA fragments these data are transferred to an attached computer with specific computer program to give the results in the form of electropherogram. Results of the unknown samples are interpreted and compared to profiles of suspected persons.
Forensic genetics includes analysis of other components of genome not only the DNA. For example mitochondrial DNA can be amplified for identification as it’s found in large copy number per cell. Mitochondrial DNA has the disadvantage of higher probability of sharing the same profile with others specially maternal relatives so databases for mitochondrial DNA are set up to control this problem. Also RNA has its role in forensic investigations. It can be extracted and amplified by reverse transcriptase quantitative PCR. RNA can be used in determination of wound age, postmortem interval, the cause of death, body fluid identification and detection of genotoxicity. Other epigenetics with forensic importance are DNA methylation and histone modifications. Methylation of genes can inhibit or stimulate gene expression leading to different phenotypes. Also histone modifications e.g. histone acetylation has similar effects on genes. Profiles of these epigenetics can be used in forensic to determine body fluids, detect genotoxicity, discriminate identical twins, determination of age, paternity testing and to authenticate a natural DNA sample.
Conclusion
Forensic genetics became an important part of forensic investigations in criminal cases. It may give a clue with other scene investigations and circumstantial evidences. The most important is DNA profile that is used in identification in civil and criminal cases. First it was invented for paternity testing then it included other cases of identification.
Not only nuclear DNA is used in forensic investigations, but also mitochondrial DNA has its role. RNA analysis shows multiple uses in the same field. Epigenetics as DNA methylation and histone modification are newly used profiles in the forensic analysis.
Advances are going on to improve genetic work to be more rapid, easy, automated and having more accurate results. The most obvious regarding this issue is microfluidic techniques that can be used for all the DNA analysis steps. There are also many other techniques developed for each step of the DNA analysis.
Recommendations
Although there are great inventions and improvements in the field of forensic genetics, there are many obstacles should be overcome.
More work is needed to improve the accuracy and speed of the analysis.
More studying of the human population genetic makeup may offer new methods of human identification and find the probability of similarity between people in their genetic material.
Strong DNA databases are available in USA provided by the FBI and in Europe. More work for collection of data and helping other countries to setup their databases and sharing of information will help solving international crimes.
In the developing countries as Egypt, the forensic genetic analysis should be more incorporated in the forensic casework and become a basic crime scene investigation. This may improve the results of criminal investigations.
There is no DNA database in Egypt due to lack of data and infrequent use of genetic analysis. A national program for DNA database should be established. Database for genetic profiles from different crime scenes will help solving other crimes.