Amelogenin
Definition
A gene on both the X and Y chromosomes used for sex determination in forensic STR kits. The X-allele amplicon is approximately 6 bp smaller than the Y-allele amplicon, producing two peaks in males and one in females. Mutations in the X amelogenin primer site can cause apparent sex-typing failures; this is documented at a population frequency of approximately 1 in 900 males.
- Location
- X and Y chromosomes (genes AMELX and AMELY)
- Primary use
- Genetic sex determination in forensic DNA profiling
- Result pattern in males
- Two peaks from different-sized PCR fragments
- Result pattern in females
- One peak (both X alleles produce the same size)
- Documented mutation frequency
- Approximately 1 in 900 males
Common questions
How does amelogenin help determine biological sex in forensic DNA analysis?+
Amelogenin is a gene found on both the X and Y chromosomes. When forensic scientists amplify DNA using PCR, the X version produces a slightly smaller fragment than the Y version. Male samples show two distinct peaks (one from each chromosome), while female samples show only one peak (both from X chromosomes). This size difference is the basis for genetic sex assignment.
Why is amelogenin included in all standard forensic DNA kits?+
Amelogenin is a reliable sex-typing marker that works across all major DNA profiling systems, from CODIS to European and Indian standards. It is particularly valuable because it works on degraded remains and sub-adult samples where morphological sex estimation might be uncertain or impossible.
What happens if amelogenin results seem inconsistent?+
Mutations in the primer binding site of amelogenin, though rare, can cause unexpected results. This happens in approximately 1 in 900 males and can produce an apparent female profile despite the individual being male. Knowing this rare failure mode helps investigators recognize and resolve ambiguous sex-typing results.
Related terms
- ESS (European Standard Set)
- The set of STR loci required for profiles entered into EU national databases participating in Prüm cross-border DNA exchange. Currently aligned with...
- Barr Body
- A condensed, transcriptionally inactive X chromosome visible in the interphase nuclei of XX individuals. In dental cells it appears as a small...
- CODIS
- The FBI's Combined DNA Index System, the US national STR-based forensic DNA database. Contains profiles from convicted offenders, arrestees, and unidentified crime-scene...
- CODIS (Combined DNA Index System)
- The FBI-managed software architecture for the US national forensic DNA database, operating through a three-tier structure of local (LDIS), state (SDIS), and...
- Discriminant Function Analysis
- A multivariate statistical technique that derives linear combinations of measurements to maximally separate two or more groups (male and female). The resulting...
- Discriminant Function Analysis (DFA)
- A multivariate statistical method that builds a weighted linear equation from measurements to classify specimens into groups (here, male or female). A...
- DNA Technology Bill 2019
- India's pending legislation proposing the creation of a national DNA database (NDDB) and a profiling regulatory framework. Passed the Lok Sabha in...
- Femoral Head Vertical Diameter
- The superoinferior diameter of the femoral head, the most reliable single postcranial sex estimation measurement. US cut-offs (Stewart 1979): below 43.5 mm...
- Geometric Morphometrics
- A method that captures biological shape as a configuration of landmark coordinates, removes position/orientation/scale differences by Procrustes superimposition, and analyses the residual...
- Heterozygosity
- The proportion of individuals in a population who carry two different alleles at a locus. A locus with high heterozygosity is more...
- Humeral Head Vertical Diameter
- The superoinferior diameter of the humeral head. US cut-offs (France 1998): below 43 mm female, above 47 mm male. Second most commonly...
- INTERPOL DNA Gateway
- INTERPOL's secure server for cross-national DNA profile comparison, hosted in Lyon. As of 2023, fifty-nine member countries contribute profiles.
Explained in these topics
- CODIS 20, the European Standard Set and India's NDIS Locus StandardsA sex-typing locus on the X and Y chromosomes. Produces X-specific and Y-specific amplicon sizes in PCR, allowing sex assignment from a DNA profile. Included i...
- Polymorphism, Heredity and the Markers that Identify a PersonA gene on both the X and Y chromosomes used for sex determination in forensic STR kits. The X-allele amplicon is approximately 6 bp smaller than the Y-allele a...
- Sex Estimation from Long Bones and the Sub-Adult Sex ProblemA protein encoded by the AMELX (X chromosome) and AMELY (Y chromosome) genes. PCR amplification produces different-sized amplicons from X and Y alleles, allowi...
- Sex Estimation from Teeth and Dental DimensionsA structural protein of developing enamel, coded by genes on both the X chromosome (AMELX) and the Y chromosome (AMELY). PCR primers spanning an intron produce...