About this Video

• Video Title: Marcadores moleculares basados en PCR: Marcadores SSR. Microsatelites | 26/95 | UPV
• Channel: Universitat Politècnica de València - UPV
• Speakers: Belen Picó
• Duration: 00:07:52

Introduction

This video describes the methodology for identifying simple sequence repeat (SSR) markers, also known as microsatellite markers. It explains SSRs, their variability, PCR amplification techniques, and their applications in genetic studies.

Key Takeaways

• SSRs (Microsatellites): These are DNA fragments with tandem repeats of 2-6 nucleotide units, repeated several to dozens of times. Their high variability makes them useful genetic markers.
• PCR Amplification: Specific primers flanking the microsatellite sequence are used to amplify the region. The amplified fragments' varying lengths (due to differing repeat numbers) create a polymorphic banding pattern.
• Variability Mechanisms: SSR length variation arises from polymerase slippage during replication and unequal crossing over, leading to the addition or deletion of repeat units.
• Visualization and Analysis: Amplified fragments are separated by electrophoresis (agarose or acrylamide gels), revealing different allele lengths. Capillary electrophoresis with fluorescently labeled primers allows multiplex analysis of several loci simultaneously.
• Advantages of SSR Markers: They are codominant (homozygotes and heterozygotes are distinguishable), highly reproducible, and widely used in genetic diversity studies. However, analyzing many loci can be expensive unless multiplex PCR is employed.

Este vídeo de la Universitat Politècnica de València explica los marcadores microsatélites (SSRs), fragmentos de ADN con repeticiones en tándem de 2 a 6 nucleótidos. Su alta variabilidad, generada por deslizamiento de la polimerasa durante la replicación y entrecruzamiento desigual, los convierte en excelentes marcadores genéticos. Se amplifican mediante PCR usando cebadores específicos que flanquean la secuencia repetida. La electroforesis (geles de agarosa o acrilamida, o electroforesis capilar con fluorocromos para análisis multiplex) separa los fragmentos según su longitud, revelando el patrón de bandas polimórficas. Los SSRs son codominantes (distinguen homocigotos y heterocigotos), altamente reproducibles y ampliamente usados en estudios de diversidad genética. Aunque analizar muchos loci puede ser costoso, la PCR multiplex permite analizar varios loci simultáneamente, reduciendo el coste. La principal limitación es la necesidad previa de conocer la secuencia flanqueante, aunque la secuenciación masiva está mitigando este problema.