A Brief Comment on Tandem Repeat's Insights

Kenneth Blum^*
*Correspondence: Kenneth Blum, Genetics Laboratory, Biotechnology Department, Agricultural University of Athens, Greece, Email:

Description

Today, forensic DNA analysis and other human identification testing applications frequently use short tandem repeat (STR) typing techniques. DNA samples containing length-variant STR alleles are typically separated by capillary electrophoresis after multiplex PCR amplification, and their genotypes are determined by comparison to an allelic ladder provided with a commercial kit. The technology and problems related to STR typing are briefly described in this article. Microsatellites (sometimes referred to as STRs), also known as simple sequence repeats [1-3] are DNA lengths that resemble an accordion. They contain core repeat units, which can range in length from two to seven nucleotides, and they are repeatedly repeated anywhere between a half-dozen and several dozen times. Although there are millions of STR markers in the human genome, only a small core group of loci have been selected for use in forensic DNA and human identity testing. Similar to employing a single, universal currency in the financial sense, core loci enable the exchange and comparison of analogous genetic data. There are currently commercial kits for creating DNA profiles with these basic STR loci.

DNA profile analysis is usually the first step in STR data interpretation. Off-scale data and the associated pull-up peaks can suggest that the multiplex PCR experiment used too much DNA template. Larger-sized STR loci with no signal suggest the presence of PCR inhibitors or damaged DNA. A potential combination can be indicated by the existence of more than two alleles at a locus, however it's important to avoid concentrating on just one locus because tri-allelic patterns could occur. When interpreting DNA mixtures, the X/Y allele ratio from the amelogenin sex-typing primer pair can be useful. An analyst can learn about probable PCR inhibition or DNA degradation from inter-locus balancing within a dye channel. A developer of a STR kit can learn information about dye sensitivity and PCR primer balance from the inter-locus balance of dye channels. This method is well-known for producing substantial satellite DNA building units [4,5]. It has to do with the movement of repeats across chromosomes that are similar. However, this process only plays a small part in STR mutation because it affects several chromosomes. However, as will be explained later, this process might be in charge of STR multistep mutations. According to this method, retrotranscripts are extended at their 3' end to form A-rich STRs, much to how mRNA is polyadenylated.

There is proof that transposable elements and the most prevalent human STRs with A-rich content are related. On the other hand, a high density of transposable elements does not always translate into a high density of STRs. If this really is the mechanism for STR mutation, more investigation is required. In accordance with this mechanism, retrotranscripts are extended at their 3' end to create A-rich STRs, much like how mRNA is polyadenylated. There is proof that transposable elements and the most prevalent human STRs with A-rich content are related. A high density of transposable elements does not necessarily translate into a high density of STRs, though. To ascertain whether this is a genuine STR mutation process, more investigation is required.

Conflict of Interest

The author declares that there is no conflict of interest associated with this paper.

References

1. Broun, Pierre and Steven D. Tanksley. "Characterization and genetic mapping of simple repeat sequences in the tomato genome." Mol Gen Genet 250 (1996): 39-49.

Google Scholar, Crossref

2. Strassmann, Joan E, C.R. Solis and K. Barefield. "Trinucleotide microsatellite loci in a swarm‐founding neotropical wasp, Parachartergus colobopterus and their usefulness in other social wasps." Mol Ecol 5 (1996): 459-461.

Google Scholar, Crossref

3. Postlethwait, John H, Stephen L. Johnson and Clare N. Midson, et al. "A genetic linkage map for the zebrafish." Science 264 (1994): 699-703.

Google Scholar, Crossref

4. Coote, T and Michael William Bruford. "Human microsatellites applicable for analysis of genetic variation in apes and Old World monkeys." J Hered 87 (1996): 406-410.

Google Scholar, Crossref

5. Ma , R.Z, I. Russ, C. Park and D.W. Heyen, et al. "Isolation and characterization of 45 polymorphic microsatellites from the bovine genome." Anim Genet 27 (1996): 43-47.

Google Scholar, Crossref