Mutants possess the X-Gene which is positioned on the twenty-third chromosome, or the sexual chromosome. The activation of the X-Gene leads to the production of the protein xenogin. Xenogin produces chemical signals inducing mutations on other genes, ending up with mutant organisms who are variously empowered.
For most mutants, their mutation occurs mostly during puberty although activation may occur earlier for some individuals. Triggers for the activation of a mutation can be stress, fear, starvation, and/or trauma.
Solar radiation has also been linked to dramatic rises in mutant birth rates. Direct radiation on humans who are latent mutants has been proven to be a factor of mutant activation. The radiation of parents has been presented as being responsible for mutant births.
A secondary mutation is a phenomenon in which an existing mutant gains additional powers or change in appearance after undergoing another X-Gene mutation. Typically, a secondary mtuation occurs within the twenties of the subject and generally appears in a time of great stress for the individual.
Children of the mutant race most often have very similar, exact duplicates, or advanced versions of one or both parents' powers, such as Regan Wyngarde, Laurie Collins, Lorna Dane, Akihiro, Kurt Wagner, Ruby Summers, and Megan Gwynn.
Neither of these results are uncommon when crossbreeding between mutants and humans. Familial power similarities are not only passed from parent to child but can also be common between siblings in first generation mutant families (i.e. Emma, Adrienne, and Cordelia Frost; Charles and Cassandra Xavier; Scott, Gabriel, and Alexander Summers). Though less common, mutations can also vary widely within first generation mutants (i.e. Sam, Paige, Melody, Jeb, Josh, Liz, Lewis, and Cissie Guthrie; Piotr, Illyana, and Mikhail Rasputin) just as with parental power inheritance.
In very rare instances, a child of two mutants can evolutionarily regress and be born as a human without an X-Gene.
It has been stated that second generation mutants could be mightier than their parents, as they possess often the addition of their parents' powers.
The mutations developed by mutants have been observed to be extremely variable, some being benign while others are malignant. They range from minor physical mutations (such as blue skin) to vastly powerful abilities (such as reality warping or telepathy). Also, some mutants experience a change in physiology and/or anatomy.
Legacy virus: The Legacy virus was an airborne plague that ripped through the mutant population, killing hundreds. The virus works by targeting the X-Factor and, when locating the X-Factor within a person, inserting introns into the DNA causing the replication and transription processes to be severely disrupted. This causes the mutant's body to become incapable of creating healthy cells, eventually resulting in the death of the mutant.
HX-N1: A synthetically engineered influenza virus that was designed as a form of mutagenic biological warfare. Designed by Lobe, it was tailor-made to affect mutants. The strain dampens the powers of mutants and robs them of their extranormal abilities, causing severe complications for those with a complete mutant physiology.
Terrigenesis: Mutants can be slowly killed by Terrigen by gradually incapacitating them. If not killed by Terrigen, mutants can be sterilized by it. If a mutant has had their abilities deactivated, Terrigen can reactivate mutant powers temporarily unless administered on a regular basis. This gradual death by Terrigenesis is called M-Pox.
- Mutants cannot acquire the AIDS virus.