DNA – Unidentified & Matching

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Unidentified decedents (UID) are people who have died and whose bodies have not been identified.

Unclaimed persons are those who have been identified by name, but for whom no next of kin or family member has been identified or located to claim the body for burial or other disposition.

The NIJ-funded National Missing and Unidentified Persons System (NamUs) is the first national online repository for missing persons and unidentified dead cases. NamUs is a free online system that can be searched by medical examiners, coroners, law enforcement officials and the general public from all over the country in hopes of resolving these cases. Anyone can search this database using characteristics such as sex, race, distinct body features and even dental information.

NamUs includes three databases:


Many times people online hope to find matches to an unidentified body found to someone missing. When comparing an Unidentified (UID) Earthly Body, or Human Remains to find a possible match to a missing person, that one suspects could be the UID, keep the following in mind:

When UID’s are found and DNA tests are completed, and show as such at NamUs

  • the POTENTIAL matches will ALWAYS be someone who has NOT had DNA testing performed.
  •   CODIS  (FBI-Combined DNA Index System) holds all the UID’s DNA and those missing who have had DNA tests completed.

The focus to finding a possible match to the UID should be on:

1. Those missing who were never DNA tested.

2. Those missing who may not be in NamUs with no DNA tested.

3. Those missing who may never have been reported missing.

4. Those missing from other countries that are here in the USA who have not had their DNA added to our CODIS system and/or whose families may not even know they are missing.

5. Those missing from the USA that may never have been reported missing.


How does the DNA process work for making an ID?

Good sources to read:


LostNMissing Unidentified: http://uidlnm.blogspot.com/

NamUs Unidentified:  https://identifyus.org/en

NamUs Missing: http://www.namus.gov/




Credit to: http://www.sfu.museum/forensics/eng/pg_media-media_pg/adn-dna/

DNA structure and function

Short for deoxyribonucleic acid, DNA is a molecule that contains the genetic code for each organism. Like a blueprint, DNA stores the essential instructions for building cells and regulating their functions.

Structurally, DNA consists of two long strands of smaller molecules called nucleotides, bound together to form a twisted ladder called a double helix (see photo).  Every nucleotide contains a phosphate molecule, a sugar molecule and one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T). Each base is bound to a complementary base on the opposite side (A with T, C with G) to form the rungs of the ladder. The human genome contains approximately 3 billion base pairs and their sequence regulates the expression of genes.

Cells contain both nuclear and mitochondrial DNA. Nuclear DNA (nDNA) is found inside the control centre of the cell: the nucleus. This DNA contains an individual’s entire genetic blueprint stored on 23 pairs of chromosomes. Mitochondrial DNA (mtDNA) refers to circular DNA stored only in structures called mitochondria that generate a cell’s energy.

Nuclear and mitochondrial DNA differ in important ways. While each cell contains only one copy of nuclear DNA, it may contain up to 10,000 copies of mitochondrial DNA. In addition, nuclear DNA is a combination both parents’ genes, while mitochondrial DNA is inherited solely from the mother.

DNA analyses

Like fingerprints, every individual possesses their own unique DNA sequence. When attempting to identify an individual, forensic investigators create a genetic profile – a set of numeric values that is exclusive to that person. To do this, DNA is first extracted from a piece of evidence. A technique known as real-time polymerase chain reaction (PCR) is then used to detect and quantify the amount of DNA available. Exact ‘copies’ are made of specific parts of the DNA using a process called amplification. Another technique called gel electrophoresis separates the different DNA parts based on size. The sample is searched for special areas of DNA that repeat themselves. Although humans share over 99% of their DNA, these particular segments, called Short Tandem Repeats (STR), vary between individuals. Because a person inherits different genes from each parent, every individual has a particular set of STR markers and the chance of two unrelated people having the same pattern is very low. As a result, DNA ‘profiles’ can be used to assist in the identification process.

Sex identification is an important part of generating a DNA profile. To determine sex from nDNA, analysts use the fact that females have two X chromosomes and males have one X and one Y chromosome to target genes that differ between males and females. Three common techniques in forensics focus on the SRY gene, the amelogenin gene and repetitive sequences on the Y-chromosome (Y-STR).

The SRY gene is responsible for the development of a fetus into a male. As a result, its presence suggests a male individual, while its absence suggests a female. The amelogenin technique targets a gene that is found on both the X and Y-chromosomes. However, the gene sequence is longer in males than females and once visualized, the length can be used to determine the sex of the individual.  The Y-STR technique targets DNA on the nuclear genome specifically. This technique looks for short repeats of the Y-chromosome that are only present in males. Since males inherit this portion of their Y-chromosome from their fathers, this technique can be used to test paternal relationships.

Mitochondrial DNA can also be used to explore family relationships, but because it is passed exclusively from mother to child, it traces only the female line. The higher copy number in mDNA also allows more DNA to be recovered for analysis, making mitochondrial DNA particularly useful for analysing degraded or damaged material.

DNA degradation

Degradation refers to the breakdown or destruction of cellular structures after death. Because DNA is contained in the cell, exposure of tissues to the environment, fire, water or chemicals will eventually lead to the physical break-down of the DNA strands and the alteration of its chemical structure. These changes can lead to incorrect assignments of base pairs and the incorrect identification of a species or individual. If a sample is very degraded, DNA analysts must be careful to ensure they are testing the right material. Importantly, samples must be collected and extracted without contaminating them. Because everyone has DNA, if a sample is mishandled, DNA which does not belong to the target sample (for example from a police officer) may be detected instead. This could result in a false profile. In addition, every analysis must be repeated more than once to control for random chemical changes. Overall, DNA testing facilities must be extremely clean and follow strict protocols to ensure that the results obtained are accurate.

DNA amplification

To maximize the amount of DNA recovered from a degraded sample, extra copies of the DNA often need to be made. This is called DNA amplification. A Polymerase Chain Reaction (PCR) is an artificial method of copying DNA in a way similar to how normal cells replicate. To perform PCR, a DNA sample is combined with an enzyme, primers and other chemicals. The solution is then heated to activate the enzyme and separate the double-stranded DNA. As a new single strand detaches from the original DNA, the primers and the enzyme use free nucleotides to replicate the specific area. Repeated heating and cooling of the reaction causes the DNA to split and replicate and the whole process starts again. In subsequent cycles, the primers will target the original DNA strands as well as the recently replicated strands. In this way, thousands of copies of a small segment of DNA can be made simultaneously. Between 30 and 60 repeats are needed to replicate enough DNA for analysis, depending on the level of degradation.

DNA databases

As powerful as DNA analyses are, a DNA profile cannot identify an individual on its own. An unknown individual’s profile must be compared with DNA taken from a known source in order to make a positive identification. To facilitate rapid and accurate identifications, many countries now maintain searchable databases of large numbers of DNA profiles. When a new profile is entered into the system, it can be compared to all the other profiles and if there is a match, the system calculates the statistical significance of the result.

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