D3S1358 is one of the standard genetic markers used in forensic DNA profiling and paternity testing. It sits on chromosome 3 and belongs to a class of markers called short tandem repeats, which are tiny segments of DNA where a short sequence repeats over and over. The number of repeats you carry at D3S1358 is what shows up as a pair of numbers on your DNA test report, and that pair helps distinguish you from virtually everyone else on the planet when combined with results from other markers. The name itself is a coded label that tells scientists exactly where in the genome the marker sits and how it was originally cataloged.
Breaking Down the Name
The name D3S1358 looks like a random string of characters, but each piece carries specific meaning. The “D” stands for DNA. The “3” identifies the chromosome where the marker lives, in this case chromosome 3. The “S” means it is a single-copy sequence, meaning it appears at just one location in the genome rather than being scattered across multiple chromosomes. And “1358” is simply the catalog number assigned when researchers first registered this marker in a database of known genetic locations. So the full name translates roughly to “the 1,358th single-copy DNA marker registered on chromosome 3.” The marker maps to a specific band on the short arm of chromosome 3, designated 3p21.31 in cytogenetic notation.1Forensic Science International: Genetics. D3S1358
This naming convention applies to every STR marker you see on a DNA report. If you also see D5S818 or D7S820 listed alongside D3S1358, those refer to markers on chromosomes 5 and 7, respectively, following the same logic. Knowing the naming system can take some of the mystery out of a results page that otherwise looks like alphabet soup.
What the Numbers on Your Report Mean
At D3S1358, a small stretch of DNA contains a four-letter sequence that repeats back to back. Researchers who first sequenced the marker found that the repeating units consist of two slightly different four-letter motifs, AGAT and AGAC, strung together in a row.2PubMed. D3S1358: sequence analysis and gene frequency in a German population The total number of these repeats varies from person to person. In a German population study, researchers observed alleles ranging from 13 repeats up to 20 repeats.2PubMed. D3S1358: sequence analysis and gene frequency in a German population Rare alleles outside that range have also been documented, including an unusually large variant with 26 repeats and a small one with just 11 repeats.3PubMed. Unusual variant alleles in commonly used short tandem repeat loci4Forensic Science International: Genetics Supplement Series. Further allelic variation at the STR-loci ACTBP2 (SE33), D3S1358, D8S1132, D18S51 and D21S11
Because you inherit one copy of chromosome 3 from each parent, your DNA report will show two numbers at D3S1358. If both parents passed along the same repeat count, you might see “15, 15.” If they passed along different counts, you might see “14, 16” or “15, 18.” These numbers do not tell you anything about your health or physical traits. They are simply a measurement of how many times a particular DNA motif repeats at that spot in your genome.
Why D3S1358 Is Used in Forensic Databases
D3S1358 is part of the core marker panels used by criminal DNA databases around the world. In the United States, it is included in the Combined DNA Index System, commonly known as CODIS. European countries also adopted it as part of a recommended standard set of markers for their national databases, making it possible to compare DNA profiles across borders.5PubMed. Criminal DNA databases: the European situation The widespread adoption of commercially produced testing kits that include D3S1358 helped create this compatibility, since labs in different countries were effectively running the same analysis.6PubMed. A brief history of the formation of DNA databases in forensic science within Europe
A marker earns a spot in these panels by being highly variable across people, easy to measure accurately in a lab, and located in a part of the genome that does not overlap with other markers in the same kit. When you combine D3S1358 with the other markers in a standard kit, the overall ability to tell two unrelated people apart is staggering. A study of nine STR markers in a Japanese population, including D3S1358, found that the combined power of discrimination reached roughly one in a billion.7PubMed. Allele distribution at nine STR loci–D3S1358, vWA, FGA, TH01, TPOX, CSF1PO, D5S818, D13S317 and D7S820–in the Japanese population by multiplex PCR and capillary electrophoresis Modern kits now include 20 or more markers, pushing that number far higher. The instruments that read these markers, using a technique called capillary electrophoresis, can process multiple markers simultaneously from a single amplification, which is what makes routine forensic testing practical.8PubMed. Genotyping of forensic short tandem repeat (STR) systems based on sizing precision in a capillary electrophoresis instrument
D3S1358 in Paternity Testing
In a paternity test, the logic is straightforward. A child must have inherited one of their two D3S1358 alleles from their biological mother and the other from their biological father. If the alleged father cannot account for the allele the mother did not provide, that is a mismatch. A single mismatch at one marker does not automatically rule someone out, though, because mutations happen. The repeat count at an STR marker occasionally changes by one step when DNA is copied from parent to child.
This is not just theoretical. A paternity case involving two alleged fathers documented a one-step mutation at D3S1358 between an alleged father and a child. The lab confirmed the biological relationship using additional markers, including Y-chromosome markers that showed a perfect match.9PubMed Central. A Single Step Mutation at D3S1358 Locus in a DNA Paternity Testing with 2 Alleged Fathers A large-scale Chinese study examining over 28,000 confirmed parent-child pairs across 19 STR markers, including D3S1358, found a total of 1,665 mutations. The vast majority were single-step changes, with a small number of two-step or three-step mutations.10PubMed. Actual mutational research of 19 autosomal STRs based on restricted mutation model and big data This is why paternity labs test many markers at once. A true father might show one or even two mutations across a full panel, but a random unrelated man would fail at many markers simultaneously.
Population-level data from places like Sri Lanka have confirmed that D3S1358, along with markers like D5S818 and D8S1179, performs well for both paternity testing and individual identification, based on measures like heterozygosity and the power to exclude a falsely accused man.11Journal of the National Science Foundation of Sri Lanka. Population study of the Combined DNA Index System (CODIS) core loci D3S1358, D5S818, D8S1179 short tandem repeat (STR) polymorphisms in Sri Lanka
How Allele Frequencies Vary Across Populations
Not every repeat number at D3S1358 is equally common, and the frequency of each allele shifts depending on the population. In a Peruvian sample, allele 15 dominated at about 56%, while in a broader Hispanic reference group the same allele sat closer to 35%.12Spanish Journal of Legal Medicine. Allele frequencies of 21 autosomal STR markers in a mixed race Peruvian population applied to forensic practice In a Rwandan population, allele 16 was the most common at D3S1358, appearing in about a third of chromosomes sampled.13SpringerLink (Int J Legal Med). Allele frequencies and forensic efficiency of autosomal short tandem repeat loci in the Rwandan population A Japanese population study noted that the allele frequencies at D3S1358 and the other standard STR markers were significantly different from those of other ethnic populations.7PubMed. Allele distribution at nine STR loci–D3S1358, vWA, FGA, TH01, TPOX, CSF1PO, D5S818, D13S317 and D7S820–in the Japanese population by multiplex PCR and capillary electrophoresis Similar variation was observed in a study of Iraqi populations that compared allele distributions against samples from Turkey, Saudi Arabia, Iran, Syria, Jordan, and several other Middle Eastern countries.14PubMed. Allele frequencies of 15 autosomal STR loci in the Iraq population with comparisons to other populations from the middle-eastern region
These differences matter for forensic math. When a lab calculates the probability that a DNA match occurred by chance, it uses allele frequency tables specific to the relevant population. If the wrong table is applied, the resulting statistic could be misleadingly high or low. This is one reason forensic databases invest heavily in collecting population-specific frequency data from around the world.
What D3S1358 Does Not Reveal About You
One of the key reasons markers like D3S1358 were chosen for forensic use is that they sit in stretches of DNA that do not code for any known physical trait or medical condition. A systematic review looking for associations between forensic STR alleles and phenotype found no studies linking D3S1358 alleles or genotypes to any observable characteristic.15PubMed Central. Forensic Autosomal Short Tandem Repeats and Their Potential Association With Phenotype Your D3S1358 result will not tell a lab, an insurer, or anyone else whether you are at risk for a disease, what you look like, or how your body functions. This was a deliberate design choice. When governments and scientific bodies selected markers for criminal databases, they wanted identification tools that could not double as medical or personal profiling tools. The markers are identity tags, not health readouts.
This distinction sometimes gets lost on people who receive DNA test results and worry about what else the numbers might reveal. For D3S1358 and the other core forensic markers, the answer is reassuringly boring: they reveal almost nothing beyond who you are related to and whether your DNA was at a particular location.
Hidden Complexity Revealed by Newer Sequencing Technology
For decades, forensic labs measured D3S1358 by fragment length. Two alleles that produced fragments of the same size were considered the same allele. But newer sequencing methods that read the actual DNA letters have revealed that this approach was missing real variation. A study using next-generation sequencing found that D3S1358 was one of six markers where sequencing more than doubled the number of distinguishable alleles compared to length-based typing alone.16PubMed Central. Sequence variation of 22 autosomal STR loci detected by next generation sequencing
This happens because two people can have the same total number of repeats but different internal arrangements of the AGAT and AGAC motifs. A study of a central Indian population found that allele 15 at D3S1358 could be broken down into five distinct sequence variants, all the same length but with different internal patterns. D3S1358 showed the highest allele gain of any marker studied once sequence-level differences were taken into account.17Scientific Reports. Sequence variations, flanking region mutations, and allele frequency at 31 autosomal STRs in the central Indian population by next generation sequencing (NGS) Work on Danish samples similarly found that sequencing D3S1358 uncovered new allelic diversity invisible to traditional methods, and the researchers proposed new naming conventions to capture this sequence-level detail.18PubMed. Second generation sequencing of three STRs D3S1358, D12S391 and D21S11 in Danes and a new nomenclature for sequenced STR alleles
For the average person receiving a paternity or ancestry-adjacent DNA report, this is unlikely to change your results today. But it signals where forensic science is heading. As sequencing becomes cheaper, future DNA profiles may carry far more detailed information at each marker, making the identification power of even a single locus much greater than it currently is.
Unusual Results at D3S1358
Most people carry two alleles at D3S1358, one from each parent. Occasionally, a result shows three alleles at this marker. One documented case traced a tri-allelic pattern at D3S1358 back through a family, finding that it was inherited from a paternal grandmother.19PubMed. A case of tri-allelic pattern at locus D3S1358 on chromosome 3p21 inherited from paternal grandmother Tri-allelic patterns can result from a duplication event where a segment of chromosome 3 containing the marker gets copied, so one chromosome carries two versions while the other carries a third. These are rare, and labs have established procedures for handling them so they do not derail a paternity or forensic analysis.
On the other end of the spectrum, unusually large alleles can cause interpretation headaches. A D3S1358 allele with 26 repeats produced a fragment large enough to overlap with the size range expected for a neighboring marker in the same testing kit. Different commercial kits handled this differently, which raised concerns about whether such a variant would be correctly identified in all laboratories.3PubMed. Unusual variant alleles in commonly used short tandem repeat loci These outlier alleles are uncommon enough that most people will never encounter them, but they illustrate why forensic labs run quality checks and why unusual profiles sometimes require extra analysis.
Performance When DNA Is Damaged
Forensic investigators often work with DNA that has been degraded by heat, moisture, bacteria, or time. How well any given marker holds up under harsh conditions determines how useful it is in real casework. A study exposing bone and dental samples to extreme temperatures, ranging from 500°C to 1,250°C for varying durations, tracked which STR markers could still be detected. D3S1358 was recoverable from bone in about 42% of the tested conditions using standard primers, putting it among the markers that survived relatively well. For comparison, some markers dropped out entirely under the same conditions, while others like D16S539 held up slightly better in bone at close to 59%.20Gaceta Médica de Caracas. Bone and Dental DNA Damage Due to Extreme High-Temperature Exposure Through STR-CODIS, Y-STR and MtDNA Examinations
Dental material gave similar results for D3S1358, also around 42% detection under standard conditions. The broader takeaway from this kind of research is that no single marker is reliable enough on its own after extreme degradation, which is why forensic kits include 20 or more markers. Even if half of them drop out in a fire-damaged sample, the remaining markers may still provide enough information to attempt an identification. D3S1358 tends to fall somewhere in the middle of the pack for heat resistance, neither the first to disappear nor the last one standing.
How D3S1358 Fits Into Consumer DNA Testing
If you are seeing D3S1358 on a report, you are most likely looking at results from a forensic-style or paternity test rather than a consumer ancestry kit like those sold by major direct-to-consumer genetics companies. Ancestry and health-focused consumer tests typically use a different technology, analyzing hundreds of thousands of single-letter DNA variants across the genome rather than a small panel of STR markers. The STR-based approach, which includes D3S1358, is the standard for legal paternity testing, forensic casework, and immigration-related DNA verification.
That said, some people encounter D3S1358 through at-home paternity kits or through database services that accept raw STR profiles. If your report shows a pair of numbers at D3S1358, those numbers are simply counts of how many times that four-letter DNA motif repeats on each of your two copies of chromosome 3. A result like “15, 17” means one chromosome carries 15 repeats and the other carries 17. Together with the results from all the other markers on the panel, this creates a genetic fingerprint that is, for all practical purposes, unique to you.