Recent decades brought several important scientific discoveries to the service of the criminal law. And one of the most important methods of identification of criminal’s personality – dactylogram – was pressed by modern, far more sensitive and precise methodic of genomic fingerprinting. The cause of high specificity of the dactylogram – originality of pattern of papillary lines at the fingertips of a human – is extremely high, because only monoovular twins have significant possibility to have completely identical fingerprint patterns.
But every episode of life may modify fingerprints of one of the twins slightly and, thus, create dactyloscopic difference between these twins. Taking this fact into account makes clear that fingerprinting method was rightfully considered one of the ultimate tools for the police investigators. Still there are some difficulties concerned with fingerprinting method. Sometimes there is impossible to discover and document the fingerprints because of unfavorable environmental conditions.
Fingerprints may be destroyed occasionally or purposely by the criminals, or, even, accidentally by the police officers or experts while examiniing the crime scene. As it was said before, certain events such as burns or scars may modify papillary patterns and thus make useless fingerprints documented before. Finally, if the criminal will wear gloves on his arms while committing the crime, he will leave no fingerprints at all! These circumstances are the considerable limits of the fingerprinting method, though they do not disaffirm numerous advantages of the dactylogram.
Genomic fingerprinting has mastered some of the limits of ordinary fingerprinting. If person can manage to modify or even change his fingerprinting pattern, he will never be able to change his genetic code. And the core principle of the genomic fingerprinting, commonly named as DNA testing, is exactly the investigation of the unique DNA sequences that may never be congruent, except in the case of monoovular twins. Genetic code of a human contains more than 25 000 genes. And every gene has at the least two different forms – they are called alleles.
These forms encode the same protein or RNA structure – with slight differences though. Such differences affect the organism development and the formation of organs and tissues from the time of fertilization and embryonal development. Every unique combination of features has its origin in unique combination of genes that person had inherited from his parents. And chanses of casual exact match of every allele of more than 25 000 genes are too low to be considered real. Homo sapiens belong to the large biologic group of organisms that is called eukaryotes.
Almost every eukaryotic cell has specific structure known as nucleus which contains and protects genomic material of the cell and regulates functioning of genes by certain measures. Exceptions do exist, of course – there are some cell types that are specialized to the extreme, such as erythrocytes (also known as red blood cells) that have no nucleus in its mature form. But these cells do have a nucleus at the early phases of existence and lose it during the process of maturing.
Genomic material (DNA) in the nucleus is associated with specific proteins (histones) and organized in complicated structures that are called chromosomes. Every human cell contains 46 chromosomes, which are grouped into pairs based on their form and structure. Chromosomes of the same pair contain the same genes, but alleles of genes are not obligatory the same or different within the chromosome pair. This provides virtually inexhaustible diversity of combinations of genes within the human population.
But this is not the end. Genes in eukaryotes are built by so called mosaic principle. This means that not the all DNA sequence of any particular gene contains vital genetic information. There are two types of DNA sequences exist – coding sequences or exones that encode the fragments of the protein or RNA structure, and non-coding sequences or intrones that are simply cut out before the actual processes of synthesis of organic polymers according to the genetic information.
And while the exones sequences are important to the organism survival and though conservative to the certain point and are protected from mutations, the intrones are virtually useless for the purposes of protein synthesis and because of it are much less protected. It means that if mutation occurs in encoding sequence and it will not be repaired by the special enzymes, it will distort genetic information to the point of decreased or altered functionality of the appropriate protein and, subsequently, lead to disease, development defects and even death of the organism.
That’s why this kind of mutations is generally eliminated quickly. But if mutation will occur in the non-coding part of DNA molecule, this will not influence vital capacity of an organism, and may remain in the structure of DNA and lately be passed to the next generations of cells. These so called “silent” mutations increase already tremendous variability of the human genome in multiple times.