Increasing Efficiency of Short-Tandem-Repeat Genotyping for a Single Hair by Improving DNA Extraction: A Practical Study

Although DNA isolation using the commercial chelex 100 is inexpensive and fast, the DNA gained by this method shows a low concentration and is of poor quality in certain materials, such as hairs; high amount of DNA will also inhibit the efficiency of the PCR amplification.

In the present study, we have improved a hair DNA isolation approach based on chelex 100, where ammonium acetate was added to precipitate proteins, ethanol was used to pellet out DNA, and glycogen was applied as a carrier of successful DNA recovery.

As a result, we obtained high quality of DNA, which can be successfully used for authentic STR analysis from one single hair. We also noticed that the DNA dilution from 25 to 125 fold presented very good quality for short-tandem-repeat (STR) genotyping by only chelex 100 extraction, demonstrating the efficiency for STR genotyping can be improved by dilution of PCR inhibitors or other unknown inhibitors.

Taken together, our improved extraction and dilution of DNA would be used as an option for the application of hair STR analysis in judicial authentication and forensic sciences. This method may be usable for other samples, such as, eyelashes, eyebrows, tissues, sperms and blood samples in human and animals for STR genotype or DNA fingerprinting, and genetics diagnosis including retinal diseases.