what is it about short tandem repeat dna that makes it useful for dna fingerprinting
STR analysis STR analysis is a tool in forensic analysis that evaluates specific STR regions found on nuclear DNA. The variable (polymorphic) nature of the STR regions that are analyzed for forensic testing intensifies the discrimination between one DNA profile and another.[1] Forensic science takes advantage of the population's variability in STR lengths, enabling scientists to distinguish one DNA sample from another. The system of DNA profiling used today is based on PCR and uses simple sequences[2] or short tandem repeats (STR). This method uses highly polymorphic regions that have short repeated sequences of DNA (the most common is 4 bases repeated, but there are other lengths in use, including 3 and 5 bases). Because unrelated people almost certainly have different numbers of repeat units, STRs can be used to discriminate between unrelated individuals. These STR loci (locations on a chromosome) are targeted with sequence-specific primers and amplified using PCR. The DNA fragments that result are then separated and detected using electrophoresis. There are two common methods of separation and detection, capillary electrophoresis (CE) and gel electrophoresis.
Okazaki fragments Primase adds RNA primers onto the lagging strand, which allows synthesis of Okazaki fragments from 5' to 3'. However, primase creates RNA primers at a much lower rate than that at which DNA polymerase synthesizes DNA on the leading strand. DNA polymerase on the lagging strand also has to be continually recycled to construct Okazaki fragments following RNA primers. This makes the speed of lagging strand synthesis much lower than that of the leading strand. To solve this, primase acts as a temporary stop signal, briefly halting the progression of the replication fork during DNA replication. This molecular process prevents the leading strand from overtaking the lagging strand.[12]