what is polymerase chain reaction

PCR is an in vitro method in which a small amount of DNA can be copied many many times in a short time period. They write new content and verify and edit content received from contributors. Electrophysiological recordings from Xenopus laevis oocytes showed reduced affinity to type I (permethrin) but not type II (deltamethrin) pyrethroids in oocytes expressing the R1 allele (1016V+1534Ckdr) sodium channel compared to those expressing the SS allele (1016V+1534F) [20]. Please refer to the appropriate style manual or other sources if you have any questions. 1998;52:11926. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. Sci Rep. 2020;10:112. Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. PubMed aegypti from the Americas. Polymerase chain reaction - Simple English Wikipedia, the free encyclopedia In the former, the most common allele was S (98.3% in Arturo Segu; 95% in La Plata Cemetery and 92.5% in La Plata Zoo) (Fig. CAS PLoS Biol. Get useful, helpful and relevant health + wellness information. Linss JG, Brito L, Garcia G, Araki A, Bruno R, Lima JB, et al. 1. aegypti in Argentina in regions where this species is under different selection pressures due to the use of pyrethroids. Bookshelf Results of a recent study [12] showed that 410Lkdr augmented resistance to a pyrethroid in the field, with a significant interaction with spraying application distance. Clustal alignments of sequences obtained by Sanger sequencing and gene AAEL023266 inVectorbase for regions 1016 and 1534. : Detection of kdr single nucleotide polymorphism by melt curve analysis. Around 390 million people worldwide are infected with dengue every year. The antigen test is typically faster but is less sensitive than the PCR test. Bioscience. If you test positive for SARS-CoV-2 but you think you might have already recovered from COVID-19, please discuss with a healthcare provider. The tested mosquitoes were captured as immature stages or adults from the field. Amplicon melting temperatures (MTs) were predicted with uMELT online software (https://www.dna.utah.edu/umelt/umelt.html). aegypti to these insecticides is a cause of failure of vector control campaigns. Chen M, Du Y, Wu S, Nomura Y, Zhu G, Zhorov BS, et al. The limit of its sensitivity is a single molecule, making PCR a superb qualitative tool for the specific detection of rare DNA sequences. Polymerase chain reaction, PCR. Adults were captured in the field with aspirators, nets, or traps. -. How to pronounce polymerase chain reaction? This technique is used in labs to make billions of copies of the desired gene for research, diagnostic and therapeutic purposes. Polymerase Chain Reaction - an overview | ScienceDirect Topics There were more than 93,000 cases in the most recent outbreak, which occurred in 2023 (https://www.argentina.gob.ar/salud/epidemiologia/boletines). Hernandez JR, Longnecker M, Fredregill CL, Debboun M, Pietrantonio PV. And not all symptomatic people develop all of the symptoms listed above. To detect these, we developed a mHRM assay for the simultaneous genotyping of sites 1016 and 1534, which may be a valuable tool for the monitoring of kdr in Ae. Twenty-one samples were sequenced for the 1016 amplicon and 14 for the 1534 amplicon by using the Sanger method at Macrogen (Seoul, Korea) with the Ae1016GqPCRRv and Ae1534qPCRFwGC primers, respectively (Table 1). The test detects the presence of a virus if you have the virus at the time of the test. Saingamsook J, Saeung A, Yanola J, Lumjuan N, Walton C, Somboon P. A multiplex PCR for detection of knockdown resistance mutations, V1016G and F1534C, in pyrethroid-resistant Aedes aegypti. Initial cycle threshold value according to the timing of reverse transcriptionpolymerase chain reaction testing. All immature stages were reared to adults in the laboratory facilities of Centro de Estudios Parasitolgicos y de Vectores (CEPAVE). The site is secure. Typically, a PCR is a three-step reaction. Google Scholar. In the Americas, four kdr mutations related to the loss of pyrethroid susceptibility have been identified in Ae. Despite the extensive presence of Ae. translations for polymerase chain reaction, https://www.definitions.net/definition/polymerase+chain+reaction, polymeric methylene diphenyl diisocyanate. Daz-Nieto LM, Maci A, Perotti MA, Bern CM. In parallel, scientific effort needs to be urgently focused on the development of novel vector control alternatives which should have a low environmental impact. If your test is negative, continue to take steps to protect yourself and others from getting COVID-19. Research Techniques Made Simple: Polymerase Chain Reaction (PCR) The use of pyrethroids was prolonged in the northern region (Salta and Jujuy) because dengue epidemics have been recorded there since 1998 [32], with cases reported almost every year [33] up until the present (Bulletin of the Ministry of Health Argentina 2023). The mosquito Aedes aegypti is an urban vector of dengue and other arboviruses. Epub 2022 Feb 21. Mem Inst Oswaldo Cruz. This polymorphism in the 1528 position has been previously reported in samples from Africa and the Americas [15]. Allele-specific PCR has also been developed for this; although cheaper, it has a lower throughput, and the reaction conditions, which must be carefully determined to avoid inaccurate results, were not reproducible in different labs [25]. This mosquito was reintroduced into Argentina in 1986 and it is now established in all the northern and central provinces of the country; its southern boundary is formed by the provinces of Buenos Aires [4], Neuqun [5] and Ro Negro [6]. PCR has several applications in the area of medical and molecular biology. The Argentinean groups are members of the Argentinean Network for Research in Pesticide Resistance (RAREP). First report on knockdown resistance mutations in wild populations of Aedes aegypti from Argentina determined by a novel multiplex high-resolution melting polymerase chain reaction method. Conversely, the R1 and R2 genotypes are predominant in all the regions studied in the Americas. The .gov means its official. C Representative curve for the R1R2 genotype (grey). volume16, Articlenumber:222 (2023) We also considered the history of dengue epidemics and the consequent control of adult mosquitoes through spatial spraying with adulticides, which has been carried out more recently in Buenos Aires Metropolitan Area (rea Metropolitana de Buenos Aires; AMBA) than in the northern provinces. Laboratorio de Neurobiologa de Insectos (LNI), Centro Regional de Estudios Genmicos, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CENEXA, CONICET, La Plata, Buenos Aires, Argentina, Laboratorio de Insectos Vectores, Centro de Estudios Parasitolgicos y Vectores (CEPAVE CONICET CCT-La Plata-UNLP), La Plata, Buenos Aires, Argentina, Mara Victoria Micieli&Marina Ibez-Shimabukuro, Instituto Nacional de Parasitologa Dr. PCR -Principle, Steps, Types, Components And Applications Of PCR - BYJU'S Liew M, Pryor R, Palais R, Meadows C, Erali M, Lyon E, et al. Get tested if you have symptoms of COVID-19 or have been exposed to someone who tested positive for COVID-19. ANB has a research fellowship from CONICET. Hu Z, Du Y, Nomura Y, Dong K. A sodium channel mutation identified in Aedes aegypti selectively reduces cockroach sodium channel sensitivity to type I, but not type II pyrethroids. Detection of knockdown resistance (kdr) mutations in Anopheles gambiae: a comparison of two new high-throughput assays with existing methods. Polymerase Chain Reaction - Snapgene A negative test doesnt mean you are safe for any length of time: You can be exposed to COVID-19 after your test, get infected and spread the SARS-Cov-2 virus to others. Also, healthy people can become reinfected. Polymerase chain reaction (PCR) is a way to make many copies of a sequence of DNA (this is sometimes called 'amplifying' the DNA). https://www.definitions.net/definition/polymerase chain reaction. Given its affordability and short running time, this method can be used in control campaigns to monitor the presence and spread of kdr alleles. What is Polymerase Chain Reaction (PCR) Test Kit? Google Scholar. aegypti (aedaenav) are widely distributed in South and North America [14, 16, 17]: 1016V+1534F (susceptible); 1016V+1534Ckdr (resistant 1; R1); 1016kdr I+1534Ckdr (double mutation, resistant 2; R2). Zhorov BS, Dong K. Pyrethroids in an alphaFold2 model of the insect sodium channel. aegypti adults from Argentina for the first time in Salta Province (Salvador Mazza). Terms and Conditions, aegypti with a SS susceptible line confirmed that the three kdr genotypes conferred deltamethrin resistance to the insects, and that the R2R2 genotype conferred the highest level of resistance [19]. It is done in vitro using a primer. 2015;6:65885. Quantification of permethrin resistance and kdr alleles in Florida strains of Aedes aegypti (L.) and Aedes albopictus (Skuse). However, we have shown here that these alleles are present in regions that are more than 1500km apart, which suggests that they have a wide distribution. Unauthorized use of these marks is strictly prohibited. The melding of a technique for repeated rounds of DNA synthesis with the discovery of a thermostable DNA polymerase has given scientists the very powerful technique known as polymerase chain reaction (PCR). The frequency of each mutation was calculated by adding the number of homozygotes multiplied by 2 to the number of heterozygotes and dividing the total by the sample size multiplied by 2. Explain the use of primers in PCR The primer is an artificial strand of DNA that is made with a complimentary base sequence to the beginning of the DNA fragment to be amplified. Trust your healthcare provider to recommend the quickest, most accurate test available. In the past decades, the number of reported cases in the Americas has increased more than tenfold, to more than 16 million, from the 1.5 million cases recorded in the 1980s [1]. (https://www.scielo.br/scielo.php?pid=S0104-42302020000700880&script=sci_arttext), ways to prevent getting infected with COVID-19, Pathology & Laboratory Medicine Institute (R. Tomsich). PCR is very precise and can be used to amplify, or copy, a specific DNA target. This difference allowed the individual analysis of both polymorphic sites using two primer pairs in a single reaction. MTs were obtained for the IIS6 and IIIS6 paired amplicons with their respective variations in the 1016 and 1534 positions, and significant differences were observed in the MTs for both positions between both the homozygous and the heterozygous samples (P<0.05; n=612) (Fig. To confirm this finding, further, nationwide, studies are necessary. The method relies on thermal cycling, consisting of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA. This process can produce billions of copies quickly and efficiently. The information provided here is relevant for the rational design of control strategies in the context of integrated vector management. We used this method to infer the presence and frequencies of kdr alleles in 11 wild populations from Argentina. The role of kdr mutations in pyrethroid resistance in Ae. Correction to: contemporary status of insecticide resistance in the major Aedes vectors of arboviruses infecting humans. aegypti has been well established. Method: Harburguer L, Gonzalez PV, Zerba E. First report of adult Aedes aegypti (Diptera: Culicidae) resistance to pyrethroids in Argentina. The most widely used target nucleic acid amplification method is the polymerase chain reaction (PCR). The populations under analysis are located in geographically distant regions of the species distribution in Argentina: the northern provinces of Salta and Jujuy and the Buenos Aires Metropolitan Area. Accurate and quick tests are key to slowing the spread of COVID-19. We report, to the best of our knowledge for the first time, the presence of kdr mutations in populations of Ae. Its accurate and reliable. Polymerase Chain Reaction (PCR): Steps, Types, Applications Wuliandari JR, Lee SF, White VL, Tantowijoyo W, Hoffmann AA, Endersby-Harshman NM. Springer Nature. Cleveland Clinic Community Care puts patients first by offering comprehensive, coordinated, personalized healthcare. ANBI: performed all of the HRM experiments, analyzed the data, contributed to manuscript writing. For DNA extractions, an adapted protocol based on magnetic nanoparticles was used [29]. Google Scholar. Alternative adulticides, such as the organophosphate malathion, are not permitted for the treatment of human dwellings in Argentina, given environmental and sanitary considerations [8]. PCR can be extensively modified to perform a wide array of genetic manipulations. Contact your healthcare provider if your symptoms get worse or if you have questions or concerns. Genotype frequencies, confidence intervals for the six possible genotypes in each population and the results of the tested deviation from HardyWeinberg equilibrium are presented in Table 3. In addition, 410Lkdr is strongly associated with 1016Ikdr and 1534Ckdr in field populations. aegypti and the incidence of dengue in Argentina, the existence, abundance and distribution of kdr mutations in this mosquito have yet to be reported for the country. Trop Med Int Heal. PCR (Polymerase Chain Reaction) | Bio-Rad The PCR results are considered the most reliable method of testing for SARS-COV-2 because . PCR was invented by Kary Mullis in 1983. PLoS Negl Trop Dis. Polymerase chain reaction (abbreviated PCR) is a laboratory technique for rapidly producing (amplifying) millions to billions of copies of a specific segment of DNA, which can then be studied in greater detail. Given that the Calilegua mosquitoes were collected in a protected sylvatic area, where insecticides are not used, it is possible that individuals invaded the national park from nearby urban locations. Its principle is based on the use of DNA polymerase which is an in vitro replication of specific DNA sequences. Privacy Point mutations in the gene coding for this channel, called knockdown resistance (kdr) mutations, are associated with pyrethroid resistance. Polymerase chain reaction or PCR is a reaction that is utilised to amplify a gene or fragment of DNA of interest. In the original PCR procedure, one problem was that the DNA polymerase had to be replenished after every cycle because it is not stable at the high temperatures needed for denaturation. Fox-Lewis A, Fox-Lewis S, Beaumont J, Drinkovi D, Harrower J, Howe K, Jackson C, Rahnama F, Shilton B, Qiao H, Smith KK, Morpeth SC, Taylor S, Blakiston M, Roberts S, McAuliffe G. Pathology. Coevolution of the Ile 1016 and Cys 1534 mutations in the voltage gated sodium channel gene of Aedes aegypti in Mexico. For representative curves of the heterozygous SR1, R1R2 and the homozygous R1R1 see Additional file 1. ae Results of genotyping positions 1016 and 1534 in the voltage-gated sodium channel (Nav) gene of Aedes aegypti (aedaenav) with high-resolution melting (HRM). 8 Jul 2023. We do not endorse non-Cleveland Clinic products or services. Would you like email updates of new search results? To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Darsie R. The mosquitoes of Argentina. Dengue and severe dengue. Given their rapid lethal action, the effect of pyrethroids is known as knockdown; the single nucleotide polymorphisms of the sodium channel gene that confer resistance to pyrethroids are known as knockdown resistance (kdr) mutations [9]. Single-site HRM was used for genotyping kdr mutations in Asian populations of Ae. aegypti [21]. Polymerase chain reaction (PCR) is a chemical reaction harnessed to detect and identify trace bits of DNA, whether from a virus or bacteria to study the organism or diagnose an infection, or for forensic examination in criminal justice and archaeology. Advertising on our site helps support our mission. The polymerase chain reaction is a biochemical technology in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. PLoS Negl Trop Dis. In the other localities analyzed, the rate of the R1 allele was around 50% (55.4% in Lomas de Zamora, 55.6% in Avellaneda, 48.1% in La Matanza and 53.85% in Merlo) (Fig. Let us know if you have suggestions to improve this article (requires login). 2023 Feb 8;76(3):e148-e154. 2023 BioMed Central Ltd unless otherwise stated. CAS The PCR technique is based on the natural processes a cell uses to replicate a new DNA strand. Polymerase Chain Reaction (PCR) Test The numerical value of polymerase chain reaction in Chaldean Numerology is: 1, The numerical value of polymerase chain reaction in Pythagorean Numerology is: 6. Judicious ending of isolation based on reverse transcription-polymerase Please enable it to take advantage of the complete set of features! PCR has made it possible to generate millions of copies of a small segment of DNA. The duration of stay on a COVID-19 ward in the Ct group was 9.7 days shorter than that in controls. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Immature stages were maintained in the laboratory until they developed into adults. The polymerase chain reaction has been elaborated in many ways since its introduction and is now commonly used for a wide variety of applications including genotyping, cloning, mutation detection, sequencing, microarrays, forensics, and paternity testing. 2019;13:e0007432. SO: conceptualization, funding acquisition, writing of the manuscript. Since we're at the Genome Institute, it's worth noting that it was a fundamental technology behind the early days of the Human Genome Project. A high-resolution melting assay, based on an analysis of melting temperatures, was developed for the simultaneous genotyping of V1016I and F1534C kdr mutations. This means that the test can continue to detect fragments of SARS-CoV-2 virus even after youve recovered from COVID-19 and are no longer contagious. Given the strong association of the 410Lkdr allele with 1016Ikdr and 1534Ckdr, it may not be necessary to genotype the 410 site for resistance monitoring purposes [10]. If you develop symptoms, please call your healthcare provider or your local public health department to determine where to go for testing. The U.S. Department of Health and Human Services provides links to find community-based testing sites in your state. Insects. At the end of the cycle, which lasts about five minutes, the temperature is raised and the process begins again. Article 2a). This assay was shown to be cost-effective, and thus provides an interesting molecular tool for kdr genotyping in A. aegypti control campaigns. Melo Costa M, Campos KB, Brito LP, Roux E, Melo Rodovalho C, Bellinato DF, et al. Their association with pyrethroid resistance has been largely demonstrated in field populations throughout the Americas, and in in vitro assays. For the 1016 position, the results for all of the samples subjected to Sanger sequencing were in accordance with those obtained using mHRM (n=21), whereas for position 1534, there was agreement between the Sanger sequencing and HRM results for 12 of 14 samples (the two samples that did not agree were for heterozygous samples). One-way ANOVA followed by Tukeys multiple comparison test was used to compare MTs among different variants for positions 1016 or 1534. Most people have mild illness and can recover safely at home without medical care. Articles from Britannica Encyclopedias for elementary and high school students. Molecular evidence of sequential evolution of DDT-and pyrethroid-resistant sodium channel in Aedes aegypti. The authors declare that they have no competing interests. 2009;14:13515. The polymerase chain reaction also enables the investigators to obtain the large quantities of DNA required for multiple experiments and procedures in forensic analysis, molecular biology . This could be due to asymptomatic infection, but if you have symptoms, then this infection is called COVID-19. It is important to use these methods to obtain a complete picture of the frequencies of kdr alleles throughout the area of distribution of Ae. So you may continue to test positive if you've had COVID-19 in the distant past, even though you cant spread the SARS-CoV-2 virus to others. To confirm the mHRM results by a gold standard sequencing method, a number of samples of genomic DNA were PCR amplified for IIS6 and IIIS6 Nav segments with specific primers and subjected to direct Sanger sequencing. Despite the extensive presence of Ae. In contrast, a machine designed to carry out PCR reactions can complete many rounds of replication, producing billions of copies of a DNA fragment, in only a few hours. Developed in 1983 by Kary Mullis, PCR is now a common and often indispensable technique used in medical and biological research labs for a variety of applications. J Med Entomol. Careers. The polymerase chain reaction - PubMed Gurtler R, Cecere MC. World Health Organization: Criteria for releasing COVID-19 patients from isolation (. Mosquito samples were conserved in ethanol at 80C until genomic DNA was extracted from individual mosquitoes. The primers bind, or anneal, to the template at their complementary sites and serve as the starting point for copying. Martins AJ, Lima JBP, Peixoto AA, Valle D. Frequency of Val1016Ile mutation in the voltage-gated sodium channel gene of Aedes aegypti Brazilian populations. 1). These two short template sequences must be known so that two primersshort stretches of nucleotides that correspond to the template sequencescan be synthesized. In the context of the lack of approved alternative compounds, decision-making with regard to planned pyrethroid treatments should be both careful and rational to enable their utility to be prolonged. Please check with your healthcare provider if youre feeling unwell during the COVID-19 pandemic even if youve been vaccinated. Using a high-throughput genotyping technique such as the mHRM presented here, results can be obtained in a few hours (Table 2). Villanueva-Segura K, Ponce-Garcia G, Lopez-Monroy B, Mora-Jasso E, Perales L, Gonzalez-Santillan FJ, et al. Homozygous Val (VV), present in genotypes SS, SR1 and R1R1; heterozygous Val Ile (VI), present in genotypes SR2 and R1R2; homozygous Ile (II), present in genotype R2R2. The polymerase chain reaction enables investigators to obtain the large quantities of DNA that are required for various experiments and procedures in molecular biology, forensic analysis, evolutionary biology, and medical diagnostics. Mosq Syst. AMBA has a more recent history of dengue outbreaks, which represented 35% of the most important dengue outbreaks registered in Argentine in 2016 [35], 2020 and 2023 (Bulletin of the Ministry of Health Argentina), despite it being the most populated region of Argentina. Sci Rep. 2017;7:16021. https://doi.org/10.1038/s41598-017-16310-8. It is recommended that the use of adulticides should be restricted to periods of arbovirus epidemics [7]; for these, the neurotoxic pyrethroids are the preferred compounds, given their favorable toxicological properties. doi: 10.1093/cid/ciac600. In sum, the use of available complementary methods, including the mHRM presented here, will improve genotyping efforts in terms of time and cost. aegypti from Argentina. First, talk with your healthcare provider. Moreover, when the R2 allele was expressed in X. laevis oocytes, a higher resistance to both type I and type II pyrethroids was observed compared to when the R1 allele was expressed [21]. PCR Basics | Thermo Fisher Scientific - US We compared a Ct-based strategy using Smart Gene between March 2022 and January 2023 with a preceding control period (March 2021 to February 2022) when two consecutive negative reverse transcription-polymerase chain reaction tests using FilmArray were required for ending isolation. An official website of the United States government. Well-calibrated equipment and a third generation fluorescent double-stranded DNA dye are used in this method [26]. Cookies policy. aegypti [31], which achieved double the genotyping effort when compared with the mHRM proposed here. The polymerase chain reaction In two samples from La Plata Zoo and one from Arturo Segui, a silent substitution of thymidine to cytosine in position 1528 (Additional file 2: B) was detected. aegypti [3]. Article The cumulative number of tests was 3.7 in controls and 1.2 in the Ct group. A negative test means you probably did not have COVID-19 at the time of the test. We report a multiplex high-throughput assay based on a high-resolution melting polymerase chain reaction method for the simultaneous genotyping of V1016I and F1534C kdr mutations. This technique was developed in 1983 by Kary Mullis, an American biochemist. Aedes aegypti samples were collected as immature stages or adults from Buenos Aires Metropolitan Area and northern localities of Tartagal (Salta Province) and Calilegua (Jujuy Province). Rubio A, Cardo MV, Vezzani D, Carbajo AE. aegypti in the Americas during the last decade. What is PCR? A license is required to use the PCR process.) Hence, further studies should be undertaken for the development of mHRM that can simultaneously detect 410Lkdr, 1016Ikdr, 1534Ckdr and/or other polymorphisms of interest in the Ae. PCR relies on a thermostable DNA polymerase, Taq polymerase, and requires DNA primers designed specifically for the DNA region of interest. Polymerase chain reaction (PCR) Flashcards 1999;5:5758. The target site of pyrethroid insecticides is the voltage-gated sodium channel (Nav), a membrane protein present in excitable cells. Springer: Berlin; 2021. p. 491594. Aedes aegypti spreading in South America: new coldest and southernmost records. Mosquito sampling was performed in 2018 and 2019 in the provinces of Salta (Tartagal; S223058.9, W6348.079), Jujuy (Calilegua National Park; S233820, W645017) and Buenos Aires [La Plata (S345517.2, W 5757.272); Merlo (343955S, 584339O); Arturo Segu (345316S, 580736O); Lomas de Zamora (344600S, 582400O); Avellaneda (344000S 582100O); Quilmes (344300S, 581600O); La Matanza (344300S, 583800O) and Tigre (342500S, 583500O)] (Fig. You can also call or check the websites of your local hospitals in your health insurance network or check with community health centers or urgent care centers. 2021 Dec;93(12):6794-6797. doi: 10.1002/jmv.27206. 2018;12:117. In the urban localities, a higher frequency of R1 was detected, although it was the least common allele in Quilmes (31.7%), but the most common one in Tigre (73.4%). Biomed Res Int. All data generated or analyzed during this study are included in this published article (and its supplementary information files). Morphological identification was determined under a stereoscopic microscope by using dichotomous taxonomic keys [28]. (The PCR is covered by patents owned by Hoffman-La Roche. A standard Polymerase Chain Reaction (PCR) is an in vitro method that allows a single, short region of a DNA molecule (single gene perhaps) to be copied multiple times by Taq Polymerase. This assay was shown to be cost-effective, and thus provides an interesting molecular tool for kdr genotyping in A. aegypti control campaigns. Google Scholar. Figure2a shows representative curves of homozygous samples in both positions (SS and R2R2), and the heterozygous SR2.

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