Short Tandem Repeat (STR) analysis is a common molecular biology method used to compare allele repeats at specific loci in DNA between two or more samples.
What is the main purpose of this STR?
Abstract. Short tandem repeat (STR) analysis is an informative approach to genetic identification and is commonly associated with DNA testing in forensic laboratories, paternity disputes or missing persons cases.
How are STRs used in the crime scene investigation?
To perform a forensic DNA analysis, DNA is first extracted from a sample. Just one nanogram of DNA is usually a sufficient quantity to provide good data. The region containing each STR is then PCR amplified and resolved according to size, giving an overall profile of STR sizes (alleles).
How does STR profiling work?
STR profiling is an analytical DNA technique which PCR-amplifies variable microsatellite regions from a genomic DNA template, separates the PCR amplicons on a genetic analyzer, and uses software to analyze the resulting data and compare the data from one specimen to databases housing previously generated STR sets.
How is STR typing done?
The complete process for STR typing includes sample collection, DNA extraction, DNA quantitation, PCR amplification of multiple STR loci, STR allele separation and sizing, STR typing and profile interpretation, and a report of the statistical signifi- cance of a match (if observed).
How are STR loci named?
The STR locus is named as, for example, D3S1266, where D represents DNA, 3 means chromosome 3 on which the STR locus locates, S stands for STR, and 1266 is the unique identifier. On the basis of different repeat units, STRs can be classified into different types.
What is an STR marker?
Short tandem repeats (STRs) represent intron polymorphism among individuals that occur frequently in the human genome. The number of STR markers required for unique characterization of individuals can be predicted based on the allele frequencies in a population.
How are STRs used to identify individuals?
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. Thus STR analysis provides an excellent identification tool.
How can your DNA be used to identify you?
DNA can be used to tell people apart because humans differ from each other based on either their DNA sequences or the lengths of repeated regions of DNA. The technique of gel electrophoresis separates DNA by size, thus allowing people to be identified based on analyzing the lengths of their DNA.
What do STR kits determine?
DNA Separations Following PCR amplification, the overall length of the STR amplicon is measured to determine the number of repeats present in each allele found in the DNA profile. This length measurement is made via a sized-based separation involving gel or capillary electrophoresis (CE).
How many types of STR are there?
On the one hand, according to the length of the major repeat unit, STRs are classified into mono-, di-, tri-, tetra-, penta-, and hexanucleotide repeats. The total number of each type decreases as the size of the repeat unit increases. The most common STRs in the human genome are dinucleotide repeats (5).
What are the 13 loci?
The 13 STR loci CSF1PO, FGA, TH01, TPOX, vWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, and D21S11 have been selected as the core loci for use in CODIS (1).
How do you identify a STR marker?
The most common approach to identify STR alleles includes the in vitro amplification of STR (microsatellite) loci by the polymerase chain reaction (PCR) using primers flanking the repeat region and subsequent fragment analysis to identify the allele sizes.
What are VNTR and STR?
VNTR: VNTR is a type of tandem repeat in which a short sequence of nucleotides (10-60 base pairs) are repeated a variable number of times in a particular locus. STR: STR is a type of tandem repeat in which a short sequence of nucleotides (2-6 base pairs) are repeated a variable number of times in a particular locus.
What is an STR profile?
The most common type of DNA profiling today for criminal cases and other types of forensic uses is called STR (short tandem repeat) analysis. If that DNA base sequence is altered (or mutated, as scientists generally say), the sequence of amino acids in the resulting protein can also be altered.
What are the names of the 13 STRs?
The 13 STR loci CSF1PO, FGA, TH01, TPOX, vWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, and D21S11 have been selected as the core loci for use in CODIS (1).
What are the disadvantages of STR?
There are two main disadvantages of these genetic polymorphisms that have to be dealt with: first, the individual biostatistical efficiency of the most commonly used STR markers, as measured e.g. by its exclusion power in paternity cases, is limited (typically between 0.5 and 0.7 in trio cases); and second, STRs
What are STR markers?
Short tandem repeats (STRs) represent intron polymorphism among individuals that occur frequently in the human genome. The number of STR markers required for unique characterization of individuals can be predicted based on the allele frequencies in a population.