Microsatellite Instability

Abstract

Abstract Microsatellites, also called short tandem repeats (STR) or simple sequence repeats (SSR), are short tandemly repeated sequence motifs of 1–6 bp. They have a proprietary mutation mechanism, DNA replication slippage, which results in the gain or loss of repeat units. Because microsatellites experience a higher mutation rate than single‐copy DNA and their alleles can be easily scored without DNA sequencing, microsatellites have been a highly popular genetic marker for forensics, behavioural ecology, population and conservation genetics. Many human genetic disorders were identified by genetic mapping with microsatellites. Exceptionally long microsatellites have been found to be associated with certain human genetic disorders, such as Huntington disease, fragile X and spinocerebellar ataxia. Microsatellites are highly variable DNA stretches which mutate by changing their repeat numbers. Microsatellite polymorphisms are generated by a specific mutation process called DNA replication slippage. Microsatellites are distributed throughout the entire genome. Specific microsatellite loci are conserved across species boundaries, but ultimately they degenerate by the acquisition of base substitutions. Trinucleotide repeats are often involved in genetic disorders which can be attributed to the expansion of a trinucleotide repeat. Most simple genetic disorders in humans were mapped using polymorphic microsatellites as genetic markers. Microsatellites were highly versatile genetic markers, which allowed unprecedented insights into many research areas, such as population genetics, forensics, behavioural ecology and molecular ecology.