Mini STR Sites


Mini STR Sites

The sites in which product size is less than 200bp. When DNA is degraded and such sites are taken which are large in size then STR will not get amplified & hence allele dropout will occur. In the case of mini STRs sites closer to the STR are taken to have good prier binding. Do not design primers for flanking regions always design primers for stable site flanking sites are unstable.


A small product size will be obtained as primers are binding at the site nearer rather far apart.

Mixture Sample

In mixture, the number of repeats will be more. Peaks explain that the sample is contaminated or not. The height of peak will be different from prominent peaks smaller less not of peaks DNA is less and the copy number is less.


The peaks of contaminating DNA would be less i.e
  • Below 15% height is due to shutter product formation.
  • If more than 15% but lesser than the prominent peak then it will be a mixture.
The mixture can be resolved by comparing with the reference i.e suspects DNA because mixture peaks will include the peaks matching to that of the suspect. The number of probable contributions also has to be assessed, the ratio of individuals contributing to the mixture. It also has to be seen whether the workers handling the sample have their DNA as contamination or not.

SNPs (Single Nucleotide Polymorphism)

Most SNPs are not in use not useful to reach the individual. In order to determine the race or ethnicity of the individual. SNPs can be used. STR copy number change but SNPs do not change (maybe a change after 10 generations). In races, the changes will be different from one another but will be permanent in a single race. On the base of the sequence, it can be seen. But this is a more costly approach.

From a forensics point of view to see an individual’s origin i.e to which race he belongs one can use SNPs for shortlisting. Just like in a mixture amelogenin can tell that who are the contributors in it, either male or both similarly one SNP will be the same in all individuals as it will not change.

In mixed races, through ARMS one can tell also.


From a forensic point of view, only SNP is not an important STR analysis is important.
Y chromosome:
  • It does not have many important STR sites.
  • It has to be seen that in came how y chromosome can work.
  • To see an evolution.
  • Migration.
  • Pedigree/origin of a race.
As the y chromosome is small in size hence by having a small genomes size not many STR sites are present. Therefore, it does not have much utility in forensic.

If amelogenin is not working then through the STR site of y chromosome sexual assault is seen. It can also be used in paternity testing, missing person investigation, human migration evolution studies, historic & geological research.

Editor's Recommendation:

Mini STR Sites Mini STR Sites Reviewed by AB Ultimate Guides on June 21, 2020 Rating: 5

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