Fallout 76 mutations

General information
Mutations are a type of condition in Fallout 76.

When the player character gets exposed to radiation, they have a 5% chance per 5 HP radiated to be mutated. This can occur from being struck by excessive background radiation from an source such as zones devastated by nukes, irradiated creatures, radioactive waste etc., or by consuming radioactive food and liquids. A player character can have multiple mutations at once.

RadAway has a chance to cure a random mutation, while any radiation protection gear (e.g. hazmat suit or gas mask) reduces the chance of mutation. The Starched Genes perk will also prevent mutation but will prevent RadAway from curing acquired mutations, essentially making them permanent while the perk card is equipped. Entering a contamination chamber will cure your radiation thus removing a random mutation.

Mutations are retained when the player dies and respawns, however a small percentage of the accumulated rads are eliminated each time a death occurs. If you do not yet have the Starched Genes perk and are attempting to keep a desirable mutation, you can simply avoid using RadAway and allow yourself to be repeated killed if you need to eliminate excessive accumulated rads.

Mutations are like traits from Fallout: New Vegas in that they have both positive and negative effects, such as the Strange in Numbers perk, which will increase the positive effect of a player character's mutation by 25% when their teammates are also mutated. The Class Freak perk can also reduce the negative(s) by up to 75%, though does not diminish the effects of diseases with the Plague Walker mutation. However, some of the diseases can have their effects diminished by perks (increased hunger due to parasites via Happy Camper or All Night Long, increased limb damage via Adamantium Skeleton, etc).

The mutations Herbivore/Carnivore are mutually exclusive and cannot be obtained simultaneously.

Mutation serums can be purchased from the Whitespring Bunker once the player joins the Enclave. The MODUS science terminal vendor found in the Science Wing of the bunker, the serums available are random and located in the Aid section. The base cost is 5,000 caps.

Mutation serum recipes can be purchased from the Whitespring Bunker as well, once the player joins the Enclave. The MODUS science terminal vendor found in the Science Wing of the bunker. The serum recipes are very rare on the vendor and have a base cost of 20,000 caps.

List
A character can get infected by these mutations:

Bugs

 * Players have confirmed a bug where you WILL NOT receive the mutation from a serum if you currently have either the Carnivore or Herbivore mutations.
 * The Class Freak perk card seems to have a visual bug on the effects page of the Pip-Boy, where it isn't showing any reduction to the Empath and Herd Mentality negative effects while it is for the other mutations. This seems to only be visual though, because the Herd Mentality negative effect of having SPECIAL reduced by 2 when solo and in combination of rank 3 Class Freak doesn't reduce SPECIAL at all when equip, possibly due to rounding. Unconfirmed if the Empath negative effect is reduced or just a visual bug, but it feels like it is reduced correctly.
 * The Grounded mutation with the Class Freak perk (sometimes) says energy guns do 12% less damage (the correct amount) sometimes it says 50% less damage (the standard amount) but the energy gun damage is always 50% less.
 * The Strange in Numbers perk can increase the effect of some mutations significantly. For example, combining it with the "Bird Bones" mutation can cause the player's fall speed to be reduced so much that it is possible to walk on air.
 * The Herd Mentality mutation can prevent sharing of other perk cards with the group. This appears to be fixed in the December 11th patch 1.0.3.10