Question

4. What is a Short Tandem Repeat (STR)? Why are they important in forensic analyses? 5. In this lab, you are only looking at one STR. Is this what would happen in a real forensic case? If not, briefly explain what would happen.

Answer 1

(4)

STR (Short tandem repeats) is a genetic variant that consists of a linear repetition of a specific sequence motif. It is accordion-like regions of the human genome that differ in length through contraction or expansion between individuals based on a repeated DNA sequence. Forensic laboratories generally use tetranucleotide repeats that contain a 4bp repeat sequence like GATA.

STR analysis is an informative strategy to genetic identification and description that is generally correlated with DNA testing in forensic laboratories like missing person cases or paternity disputes. There are other uses for STR analysis also like authenticating cell lines, confirming tissue sample origins, tracing genetic mutations in research studies of diseases like cancer, detecting cell or tissue mixtures, and determining twin zygosity.

STR analysis in forensic analysis estimates specific STR domains detected on nuclear DNA. The STR regions analyzed during forensic testing which are polymorphic in nature enhances the distinction between one DNA profile and another. The population's variability in STR lengths permits scientists to differentiate different DNA samples in forensic science.

(5)

No, in a real forensic case scientists does not rely on a single STR. They rely on multiple STRs which are analyzed by the process of multiplexing that permits the synchronous analysis of multiple STRs. Thus, the potential of STR analysis arises from studying multiple STR loci simultaneously.