DNA Testing of various samples

Bloodstain on Shirt - The stain on the shirt is most likely dirty and contains degraded DNA (especially if the shirt was worn extensively) and blood is also filled with proteins that may interfere with PCR. Organic extractions involving Pk, DTT, and Phenol Chloroform is best suited for cases like these involving dirty, degraded DNA samples. A centrifugal concentrator with a specialized filter can then be used to further purify the DNA. This type of extraction is effective at separating lipids and proteins from DNA. STR analysis is then used with PCR to study short repeating units of human DNA that can then be used for identification purposes. The repeats used in STR are highly variable and offer DNA testing results that are often statistically favorable to many other test methods. STR testing uses PCR which also requires less DNA than many other methods.

Stamp - Most stamps, except the more recent self-sticking stamps, require moistening to be stuck to a surface. This is most commonly done by licking the stamp, which could leave saliva possibly containing DNA on the stamp. The DNA in saliva, similarly to blood, can most effectively analyzed using Organic extraction followed by STR analysis of the DNA. The stamp, like the blood, most likely contains degraded DNA. Therefore PCR, which requires less DNA, would be the most applicable method.

Hair Shaft (no root) - A hair shaft without root material contains no nucleus and therefore no nuclear DNA. It is impossible to obtain any DNA that is useful for a paternity test form this sample. When collecting hair samples suitable for DNA analysis, one should look closely to find hairs with the root still attached. The root will look like a ball on the end of the hair shaft. A small cylindrical shaped covering on the end of the hair shaft is not a root and will not have adequate DNA for paternity testing. The hair must have the round shape root in order to be useful for DNA paternity testing.

Vaginal Swab Containing Semen – This sample contains both male and female cells. If sperm cells are present then it is possible to separate the sperm cells from the other cells (epithelial cells) that are present on the swab. A differential extraction procedure is used for this evidence. A differential extraction is designed to separate sperm cells from epithelial cell. However, this type of extraction often leads to mixture profiles which can be complicated and time consuming for DNA analysts. In order to eliminate mixture DNA profiles, some laboratories us the ERASE sperm isolation kit. This kit effectively and efficiently eliminates epithelial cell DNA from samples containing mixtures of sperm cells and epithelial cells. Erase makes it possible to obtain a male autosomal profile from samples that would be expected to yield a mixture profile. Using the Erase sperm isolation kit saves a great deal of time in the laboratory and a non-mixture profile is much easier to present in the courtroom.