Ministr (Reduced-Size) STR
Definition
A short tandem repeat assay redesigned so that the amplicon spans a shorter distance from primer to primer, typically less than 200 base pairs. Ministr assays recover profiles from severely fragmented DNA that standard STR kits (amplicons up to 400 base pairs) fail to amplify.
- Typical amplicon size
- Under 200 base pairs
- Standard STR amplicon size
- Up to about 400 base pairs
- Best suited for
- Severely degraded or fragmented DNA
- Design change
- Primers relocated closer to the repeat region
Common questions
Why does shortening the amplicon help recover profiles from degraded DNA?+
Environmental and enzymatic degradation breaks DNA into progressively shorter fragments over time. A shorter primer-to-primer distance means a target region is more likely to survive intact within a fragmented template, so ministr assays succeed where a standard, longer amplicon fails.
Does using ministr assays change the resulting genotype at a given locus?+
No. The repeat region and its allele calls are the same as with standard kits; only the flanking primer positions change to shrink the amplicon. Results from ministr and standard kits at the same locus should be concordant.
Are ministr kits used routinely, or only in specific casework?+
They are generally reserved for samples where standard kits give partial or no profile, such as highly degraded remains, aged bone, or fire-damaged evidence, rather than being used as a first-line default across all casework.
Related terms
- 8-Oxoguanine
- An oxidised form of guanine produced by reactive oxygen species attacking the C8 position of the guanine ring. 8-Oxoguanine mispairs with adenine...
- Abasic Site
- A position in the DNA backbone where the nitrogenous base has been lost, leaving only the deoxyribose-phosphate scaffold. Also called an AP...
- Depurination
- Hydrolytic cleavage of the N-glycosidic bond between deoxyribose and a purine base (adenine or guanine), generating an abasic (apurinic) site. Abasic sites...
- Internal Positive Control (IPC)
- An exogenous DNA template of known sequence and concentration added to the PCR reaction alongside the forensic sample. If the IPC fails...
- PCR Inhibitor
- A co-extracted substance that interferes with Taq polymerase activity or primer annealing. Common inhibitors in forensic samples include haemoglobin (from blood on...