Second Generation Multiplex Plus (SGM Plus), is a DNA profiling system developed by

Applied Biosystems Applied Biosystems is one of various brands under the Life Technologies brand of Thermo Fisher Scientific corporation. The brand is focused on integrated systems for genetic analysis, which include computerized machines and the consumables used w ...

. It is an updated version of Second Generation Multiplex. SGM Plus has been used by the

UK National DNA Database The United Kingdom National DNA Database (NDNAD; officially the ''UK National Criminal Intelligence DNA Database'') is a national DNA Database that was set up in 1995. In 2005 it had 3.1 million profiles and in 2020 it had 6.6 million profiles ...

since 1998. An SGM Plus profile consists of a list of 10 number pairs, one number pair for each of 10

genetic marker A genetic marker is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can be ...

s, along with two letters (XX or XY) which show the result of the

Amelogenin Amelogenins are a group of protein isoforms produced by alternative splicing or proteolysis from the ''AMELX'' gene, on the X chromosome, and also the ''AMELY'' gene in males, on the Y chromosome. They are involved in amelogenesis, the developme ...

sex indicating test. Each number pair denotes the two

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

values for the marker - one value is inherited from each of the subject's parents. If both alleles are the same, then only a single number, rather than a pair, is recorded.

Genetic markers

The genetic markers (or loci) used by SGM Plus are all

short tandem repeat A microsatellite is a tract of repetitive DNA in which certain DNA motifs (ranging in length from one to six or more base pairs) are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organism's genome. ...

s (STRs). The markers used are: VWA, D8S1179, D21S11, D18S51, TH01, FGA, D3S1358, D16S539, D2S1338 and D19S433. Where a marker's designation begins with D, the digits immediately following the D indicate the

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

that contains the marker. For example, D21S11 is on

chromosome 21 Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, with 48 million base pairs (the building material of DNA) representing about 1.5 percent of the total DNA in cells. M ...

. SGM Plus also uses the

amelogenin Amelogenins are a group of protein isoforms produced by alternative splicing or proteolysis from the ''AMELX'' gene, on the X chromosome, and also the ''AMELY'' gene in males, on the Y chromosome. They are involved in amelogenesis, the developme ...

(amelo) sex-indicating test. SGM Plus differs from SGM in that SGM does not use the markers D3S1358, D16S539, D2S1338 and D19S433. SGM Plus has eight markers in common with

CODIS The Combined DNA Index System (CODIS) is the United States national DNA database created and maintained by the Federal Bureau of Investigation. CODIS consists of three levels of information; Local DNA Index Systems (LDIS) where DNA profiles ori ...

FGA, TH01, VWA, D3S1358, D8S1179, D16S539, D18S51, and D21S11. It differs from CODIS in that it uses the additional markers D2S1338 and D19S433 and does not use the five markers CSF1PO, TPOX, D5S818, D7S820, D13S317.

Dye tags

The primers are tagged with the following fluorescent dyes for detection under electrophoresis: *5-FAM *JOE *NED The primers for each locus are arranged on the dyes in the following order, from low molecular weight to large molecular weight: *5-FAM: D3, VWA, D16, D2 *JOE: Amelo, D8, D21, D18 *NED: D19, THO, FGA The dyes to which each primer is attached differ from those of the original SGM DNA profiling system.

Example SGM Plus profile

The SGM Plus profile of subject GT36865 from a

National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...

paper is given below: An SGM Plus profile retrieved from a DNA database would just list the allele values: 15,18; 6,9; 11,13; 22,22; 31,32.2; 14,17; 17,20; 11,12; 13,16.3; 15,16; XY Each value is the number of

tandem repeat Tandem repeats occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other. Several protein domains also form tandem repeats within their amino acid primary structure, such as armadil ...

s within the allele. A non-standard repeat is designated by the number of complete repeat units and the number of base pairs of the partial repeat, separated by a decimal point.

Probability of Identity

The probability of identify (also known as the random match probability) is the probability that two individuals selected at random will have an identical genetic profile. Applied Biosystems estimates the probability of identity for SGM Plus to be approximately 1 in 13 trillion for African-Americans and 1 in 3.3 trillion Caucasian Americans. The

Human Genetics Commission The Human Genetics Commission (HGC) was an advisory non-departmental public body that advised the UK government on the ethical and social aspects of genetics. This included genetic testing, cloning and other aspects of molecular medicine. The Comm ...

has reported that the random match probability is in the region of 1 in a trillion. However it stated "When the SGM Plus profiling system was first introduced, there was agreement within the scientific community that identifications with match probabilities lower than one in a billion would not be quoted in the courts of law, so as to avoid overstating the value of the DNA evidence to take into account that match probabilities are only estimates, and to make sure that the figure used was one that was meaningful to non-specialists." The UK

Crown Prosecution Service The Crown Prosecution Service (CPS) is the principal public agency for conducting criminal prosecutions in England and Wales. It is headed by the Director of Public Prosecutions. The main responsibilities of the CPS are to provide legal advi ...

states "SGM Plus DNA profiling is very discriminating between individuals. The probability of obtaining a match between the profiles of two unrelated individuals by chance is very low, of the order of 1 in a billion. However, it has not yet been possible to carry out the required statistical testing to be able to quote this match probability, and in practice a more conservative chance match figure of 1 in 1,000 million is used."

References

External links