Is it Possible that DNA Genetic Material itself to fool the Definite Determination?           Part 5

Lawyers shall stand on their toes on floor to question the protocols used by laboratories, 

Eukaryotic cells heavily depended on noncoding codon triplets for their survival as well as to wither the environmental impacts through following biological functions. Some noncoding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, ribosomal RNA, and regulatory RNAs). Other functions of noncoding DNA include the transcriptional and translational regulation of protein-coding sequences, scaffold attachment regions, origins of DNA replication, centromeres and telomeres.- defense system of genes as well as to preserve  the individuality of chromosome within the sets of chromosome in the cell nucleus. These telomere codons are common to all vertebrate animals, the sequence of nucleotides in telomeres is TTAGGG. This sequence of TTAGGG is repeated approximately 2,500 times in humans.  In forensic science these noncoding codon triplets are known as INTRONS, though in molecular biology and in genetics it covers the noncoding codon triplets as well as the all RNAs it can be transcribed into and the codons the RNA contains. In forensic and anthropological investigations, DNA introns are targeted for whatever procedure– RLFP or PCR or STR is applied for many reasons.

Using the noncoding introns for forensic science – was an accidental invention; researchers were working for variation for individuality amongst only 0.1% variant for human population for the entire globe.- since 99.9% of human DNA coding sequences are the same in every person, but enough of the DNA is different that it is possible to distinguish one individual from another, unless they are monozygotic ("identical") twins due to one fertilized egg blasting into two before going through embryonic transformation and both becoming two full embryos as normal.

Alec Jeffrey and members of his Forensic laboratory at the University of Leicester in the UK working with normal genes of codons RLFP analysis, suddenly found stretches of repetitive codons of DNA differ in length in the analytical output. Usual targets for analysis in the coding codons were of repetitive sequences known as Alleles – RLFP analysis of these alleles between two loci* are short repetitive and inconclusive due to mutations  (sudden favourable or unfavorable change of DNA sequences for living cell  during the process of replication of DNA) etc. compelling the workers to go for multiple loci analysis. *The specific location or position of a gene, on a chromosome known as locus (plural loci) – in DNA set of Triplet codon representing a gene.

But on that day analytical result of repetitive sequences of Alleles were of lengthy as well as surprisingly very conclusive as well, and later it was found they have performed analysis on a “wrong” target of noncoding introns – but for setting in motion a  miraculous corrective pathway for forensic biological science. These repetitive loci were used as targets for the first generation of genetic fingerprints using the most first DNA profiling analytical method, Restriction Fragment Length polymorphism (RFLP) of variable loci. A new era in criminal investigation had begun and use of Introns as analytical target became ethical as well.

The basic technique for Restriction Fragment Length polymorphism (RFLP)

1. fragmenting the  extracted of DNA from a biological  sample by a restriction enzyme, which can recognize and cut DNA wherever a specific short sequence occurs, in a process known as a restriction digest.

2. The resulting DNA fragments are then separated by length through a process known as agarose gel electrophoresis. A method to segregate biochemicals via electrical charge.  

3. The separated fragments are then transferred to a nitrocellulose or nylon filter; this procedure is called a Southern blot. The DNA fragments within the blot are permanently fixed to the filter, and the DNA strands are denatured (disfigured)

4. Hybridization of the membrane to a labeled DNA probe; Radiolabeled probe molecules are then added that are complementary to sequences in the genome that contain repeat sequences. These repeat sequences tend to vary in length among different individuals and are called variable number tandem repeat sequences or VNTRs.

5. The probe molecules hybridize to DNA fragments containing the repeat sequences and excess probe molecules are washed away.

6. The blot is then exposed to an X-ray film. Fragments of DNA that have bound to the probe molecules appear as dark bands on the film.

This probe was not too specific, and therefore bound against multiple repetitive sites, and led into obtain the Traders’ Bar-Code pattern that many people know, and now identify, as a DNA fingerprint The more bands are shared between two individuals, the closer they are!

 

The banding pattern of a genetic fingerprint is nothing more than a bar code that is unique for just one person on earth—with the only exception of monozygotic twins who need to be distinguished by more advanced methods on the molecular level and thus various DNA analytical methods could be employed to obtain it.

Until around 1991, forensic biologists needed large amounts of high-molecular DNA for the multi-locus RFLP ‘fingerprints, practically this meant relatively that a large amount of biological samples had to be recovered. A further drawback in the early years was a lack of safe bio-statistics and laboratory standards.

Instead of further dealing with complex properties of multiple loci—size, bio-statistics and inheritance—laboratories now performs RFLPs of just one variable locus per probe as it was much easier to determine their fragment length. Since the ‘single locus’ probes could easily be washed off the nylon membrane, and then another probe for another ‘single’ locus could be hybridised against the RFLP, the information content of single-locus DNA typing remained high. The Southern blot technique is laborious, and requires large amounts of un-degraded sample DNA and very is time consuming in months as well. These early techniques have been succeeded by PCR-based assays.

Historically the dramatic change in forensic biolgy does not occur solely by the virtuous of analytical target of introns alone; but by the remarkable improvements in extraction of DNA from nearly any biological sample, no matter how small it is. DNA can now be extracted from practically any biological substance left at a scene of crime or an accident, including teeth, blood, sperm, saliva, bones, hair, urine and feaces, added to this list  is revolutionary ability, to recover DNA from inert objects that could have used by the suspects, that could lead to solve the crimes. Any laboratory dealing with DNA test should be competent enough in this aspect first and further most.