---
title: STR markers
description: A short tandem repeat (STR or microsatellite) is a pattern of two or more nucleotides that are repeated directly adjacent to each other.
---

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# [STR markers](https://devyser.com/blog/str-markers)

 Written by [Admin](https://devyser.com/blog/author/admin) | Oct 3, 2022 8:49:02 AM

A short tandem repeat (STR or microsatellite) is a pattern of two or more nucleotides that are repeated directly adjacent to each other.

The repeats can range in length from 2 to 6 base pairs/repeat. A short tandem repeat polymorphism occurs when homologous STR loci differ in the number of repeats between individuals. By identifying repeats of a specific sequence at specific locations in the genome, it is possible to create a genetic profile of an individual.

When running a [QF-PCR assay](https://www.devyser.com/knowledge-hub/principles-of-qf-pcr), STRs are amplified by PCR using the unique sequences of flanking regions as primers. By using fluorescently labelled primers amplified STRs can be identified and quantified on a capillary electrophoresis instrument.

## Stutter peaks from STR markers

Stutter peaks are peaks that may be detected primarily one repeat shorter than the true allele. They appear as a result of strand slippage during DNA synthesis. Stutter is less pronounced with larger repeat unit sizes (di- > tri- > tetra repeats). Devyser’s QF-PCR kits include only tetra repeat STRs and the STRs have been carefully selected to provide maximum informativity while generating minimal amount of stutter products.

[View full post](https://devyser.com/blog/str-markers)

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