Hello, in your question, it was my first time encountering the word T ARMs PCR. From the article, I found that T-ARMS PCyR (Tetra-primer ARMS-PCR) is a single-step genotyping method for detecting single nucleotide polymorphisms (SNPs). It involves a single PCR reaction using four primers to amplify specific DNA fragments, which can reveal the presence of different alleles. The four primers include two outer primers (Outer Forward and Outer Reverse) that amplify a larger region around the SNP as a control and two inner primers (Inner Forward and Inner Reverse) that are allele-specific, amplifying smaller fragments to indicate the presence of either the wild-type or mutant allele. Depending on the genotype, the PCR will produce a distinct pattern of three possible products: a large fragment for the control and smaller allele-specific fragments that help identify whether the sample is homozygous wild-type, heterozygous, or homozygous mutant.

After PCR, the amplicons are separated by gel electrophoresis to observe the characteristic band patterns: the wild-type homozygous genotype will show bands for the control fragment and one allele-specific fragment, the heterozygous genotype will show bands for the control and both allele-specific fragments, and the mutant homozygous genotype will display the control fragment along with the other allele-specific fragment. The choice of polymerase affects the reaction's accuracy and efficiency. Traditional Taq polymerase, with 5′–3′ exonuclease activity, can cause non-specific bands and often requires the use of DMSO for stabilization, especially in GC-rich regions. In contrast, SD polymerase, which has strong strand displacement activity but lacks exonuclease activity, minimizes non-specific bands and performs well across a wider range of temperatures (50-60°C) without the need for PCR enhancers like DMSO. This flexibility makes T-ARMS PCR a cost-effective and straightforward genotyping method, although careful optimization is still required depending on the specific conditions and polymerase used.

Reference: Alyethodi, R. R., Singh, U., Kumar, S., Alex, R., Deb, R., Sengar, G. S., Raja, T. V., & Prakash, B. (2018, February 15). T-arms PCR genotyping of SNP RS445709131 using thermostable strand displacement polymerase - BMC research notes. BioMed Central. https://bmcresnotes.biomedcentral.com/articles/10.1186/s13104-018-3236-6

Aliaa khauon Lafta , the above explanation is correct for the background information and principle. While performing the T-ARMS-PCR make sure that your primers are specific, and all four primers anneal at same or similar temperature. Avoid any secondary structure formation of your primers, along with the above-mentioned parameters. To be able to resolve in agarose gel, it is better to keep the amplicon sizes of two allele with a difference of at least 50bp or more.

While performing the PCR: please check the individual primers (allele specific) and always use controls. To my experience, I found that the optimization steps are crucial than actually performing the optimized procedure.

Tetra ARMS PCR uses four primers, two allele specific primers (Forward inner and Reverse inner) and two non-allele specific primers (Forward outer and Reverse outer). The outer primers can amplify specific fragmented portion of DNA sequences with specific size that contains SNP of interest. The inner primers then can detect the presence of SNP. If SNP is present they produce 'x' size fragments and if not, they produce 'y' size fragments. Overall procedure only takes single PCR and agarose gel electrophoresis to determine the presence of targeted SNP in a gene. No digestion with restriction enzyme is required.

Tetra arms pcr work on the principle of 4 primers as everyone told u 2 are allele specific that are inner primer other 2 are non allele specific . From the 2 inner primer one is for wild type or normal allele and other one is for mutant and variant allele. We can also call it SNP specific pcr. Arms pcr gives us 3 product in case of heterozygous condition Fo+Ro, fo+Ri, Ro+Fi. In homozygous condition there are onle 2 product size.