Gene Mods or Genetic Modifications (aka G-Mods) are new upgrades that can be taken by soldiers in XCOM: Enemy Within.

XCOM Database[]

Up to five genetic modifications may be applied to a single soldier. They modify a variety of human anatomical systems, yielding different tactical advantages. Performing alien autopsies can result in access to new genetic modifications.

– XCOM Database, XCOM: Enemy Within

Genetic Modification[]

Using Meld to organically fuse elements of alien genetic adaptions into a soldier's body, Gene Mods grant the individual new super-human capabilities. Gene Mods are applied at the Genetics Lab, which can modify up to three soldiers at a time. Soldiers are removed from active duty for three days for each Gene Mod applied.

Gene Mods can be administered to any soldier except MEC Troopers. Soldiers with Gene Mods can undergo psionic testing and the genetic modifications stack with psi abilities. The Second Wave option "Mind Hates Matter" can be enabled to prevent this combination.

Gene Mods[]

Applying a Gene Mod costs 15 to §150, 5 to Meld65 and it takes 3 days for each. One Gene Mod can be applied to each of the following areas of a soldier's body:

Type Mod Description
Brain Neural Feedback Icon.png  Neural Feedback Causes damage to psi attackers and puts all of their psi attacks on cooldown. Does not reduce the attacker's chance of success.

Neural Damping Icon.png  Neural Damping Grants a soldier +20 Will when defending against a psionic attack, and becomes panic immune. If the soldier is successfully Mind Controlled, the control is cancelled and the soldier is rendered unconscious for one turn.

Eyes Hyper Reactive Pupils Icon.png  Hyper Reactive Pupils Grants a +10 Aim bonus after missing a shot.

Depth Perception Icon.png  Depth Perception Gives additional +5 Aim and +5 Critical Chance bonuses for height advantage.

Chest Adrenal Neurosympathy Icon.png  Adrenal Neurosympathy Grants a Combat Pheromones boost that increases Aim, Crit Chance, and mobility of nearby soldiers when killing an enemy. Can only occur once per 5 turns.

Secondary Heart Icon.png  Secondary Heart Causes a soldier to be critically wounded instead of dying when reaching 0 HP. Additionally, extends bleed-out timer by 2 turns and the permanent Will penalty is negated.

Skin Bioeletric Skin Icon.png  Bioelectric Skin Hidden enemies (either in the fog of war or cloaked), within a short distance, are revealed with a vague bioelectric outline. Also grants immunity to strangulation.

Mimetic Skin Icon.png  Mimetic Skin Confers the ability to change skin pattern to match cover. When a soldier moves to high cover, enemies without special abilities will not target soldier. Does not work if any enemies have line of sight to the soldier's starting position. Leaving cover or firing will break this concealment.

Legs Boosted Muscle Fiber Icon.png  Muscle Fiber Density Confers superhuman leg strength, enabling the soldier to reach high positions without the need for ladders or other climbing aids.

Adaptive Bone Marrow Icon.png  Adaptive Bone Marrow Wound recovery time is reduced by 66%. Soldier regenerates 2 HP per turn up to the HP max without armor.

EXALT Gene Mods[]

Main article: EXALT#Gene Mods

Gene Mod Comparisons[]

The following is a comparison of the rival Gene Mods for each body section. It should be noted that Gene Mods can be swapped at a latter time for their normal cost.

Neural Feedback vs Neural Damping[]

The usefulness of either mod is entirely dependent upon the presence and perceived threat level of psionic foes (Sectoid CommandersEthereals). Generally, it's best to spend Meld on other gene mods mid-to-late game.

  • Neural Feedback causes damage to psi attackers and puts all of their psi attacks on cooldown. Does not reduce the attacker's chance of success.
    • Neural Feedback provides a greater advantage against psi attackers; in the late game, squad composition should, circumstances permitting, consist of at least one soldier with Lead By Example and a Mind Shield. If the leader is a psionic, s/he can also equip Psi Armor for a further Will boost.
    • Neural Feedback will always damage the psi attacker and force all their psi abilities on cooldown, regardless of whether the psi attack was successful or not.
      • Neural Feedback renders an Ethereal into a walking target (all their abilities are Psi-based, with no exception), allowing other squad members to easily close in without further risk.
  • Neural Damping confers +20 Will to soldiers against psi attacks and provides immunity to Panic and Mind Control; a successful Mind Control is cancelled and the soldier is rendered unconscious for one turn.
    • Neural Damping is more expensive, but does not prevent Ethereals from using other dangerous psi abilities (Psi LanceRift). Though it does reduce their damage due to the +20 Will it confers.

Hyper Reactive Pupils vs Depth Perception[]

Both mods are useful for their respective candidates and make good choices for early application.

  • Depth Perception confers additional +5 Aim and +5 Crit Chance bonuses for height advantage.
    • Depth Perception synergises with elevated firing positions; when combined with S.C.O.P.E. and Damn Good Ground the stacked bonuses allows for great accuracy increase.
    • Synergises with Muscle Fiber Density mod, which helps soldiers achieve a height advantage required to activate this mod.

Adrenal Neurosympathy vs Secondary Heart[]

Neither gene mod is particularly powerful or dramatically better than the other, though each is more suited to certain roles. Generally, it's best to spend Meld on other gene mods in the early game.

  • Adrenal Neurosympathy confers +10 Aim, +1 Movement, +5% Critical Chance and removes panic from LoS allies (within 13-tile radius) once every 5 turns after a kill.
    • Adrenal Neurosympathy is less expensive and never completely stops being useful, but doesn't stack with itself; when given to multiple soldiers, the frequency of activation will only reset its duration.
      • Adrenal Neurosympathy helps Rookies and Squaddies get the first few crucial kills they need to quickly gain promotions.
      • Adrenal Neurosympathy is useless for soldiers that do not prioritize kills (i.e. Flush, Suppression, Disabling Shot).
    • Adrenal Neurosympathy can be a determining factor in a soldier's effectiveness in killing targets of interest, or positioning themselves behind better cover. Due to the bonus only occurring once every 5 turns after a kill, the chances of the bonus getting conferred is highly unpredictable.
  • Secondary Heart causes a soldier that takes lethal damage to be reduced to critically wounded instead and extends bleed out timer by 2 turns. Soldiers that survive will also not lose Will from critical wounds. (Ensure a Medikit is available to stabilize or revive the soldier afterwards).
    • Secondary Heart only protects against the first lethal shot in a mission.
      • Secondary Heart does not defend against AoE damage (e.g. grenades) when critically wounded.
      • Secondary Heart does not defend against Chryssalids and the Sectopods using Cluster Bomb (Only applies to the bomb which put-down the soldier, and thus does not prevent additional bombs from finishing them-off).
      • Secondary Heart's usefulness diminishes with the development of Titan Armor, Plasma Weapons, Mimetic Skin and Muscle Fiber Density.
    • Secondary Heart is of no value if the soldier is never downed.
      • Secondary Heart allows a Mind Controlled ally to be taken down without concern and then revived afterwards.
    • Secondary Heart is most useful in Ironman mode, allowing for less dead soldiers overall, less units losing will and in general helping mitigating the otherwise permanent harrowing consequences of an unfortunate battle.

Muscle Fiber Density vs Adaptive Bone Marrow[]

Both mods are useful for their respective candidates and make good choices for early application.

  • Muscle Fiber Density confers superhuman leg strength, enabling the soldier to reach elevated positions without the need for climbing aids.
    • Muscle Fiber Density indirectly optimizes mobility and lethality by enhancing a soldier's ability to find elevated cover and firing positions, and reduces reliance on armors with a grapple or flight system.
    • Synergises well with Depth Perception gene mod, further increasing the benefit of elevated positions.
  • Adaptive Bone Marrow confers reduction in recovery time for injuries by 66% (stacks with Rapid Recovery) and allows a soldier to regenerate 2 HP per turn (up to their max HP without armor).
    • Adaptive Bone Marrow's recovery and durability significantly reduces downtime between missions.
      • Adaptive Bone Marrow supplements (cannot replace) the need to expend invaluable healing options (Restorative Mists MEC, Savior Support) outside of combat.
      • Adaptive Bone Marrow, Mimetic Skin and Secondary Heart are best applied to Covert Operatives and psionic squad leaders.

Bioelectric Skin vs Mimetic Skin[]

Both mods are useful and make good choices for early application, but Mimetic Skin is not recommended for soldiers who will wear Ghost Armor.

  • Bioelectric Skin reveals hidden enemies (either in the fog of war or cloaked) within a short distance, marking their locations with a vague bioelectric outline. Also grants immunity to strangulation.
    • Bioelectric Skin exposes the positions of enemies, but does not reveal enemy type or their LoS.
      • Bioelectrically marked enemies can still be triggered by soldiers as they move between cover when attempting an ambush.
    • Bioelectric Skin reveals Seekers and prevents strangulation. A single Bioelectric Skin soldier per squad eliminates the lethal cloaking advantage of Seekers (the main drivers for Bioelectric Skin).
      • Bioelectric Skin is only available after facing Chryssalids, by which point better options are available to minimize Seeker impact that do not cost Meld.
      • Bioelectric Skin's usefulness diminishes as Seekers become rarer late game.
  • Mimetic Skin confers the ability for a soldiers to conceal themselves when moving to high cover leaving enemies unable to target them. Does not work if any enemies have Line of Sight to the soldier's starting position. Leaving cover or firing will break this concealment.
    • Actions that do not drop stealth mode include:
      • Going into Overwatch (but firing an Overwatch shot will)
      • Tossing a Grenade (i.e. Flashbang, Mimic Beacon)
      • Reloading the soldier's weapon
      • Applying a Medikit or Combat Stims
      • Psi Inspiration
    • Mimetic Skin is the most powerful gene mod (when properly utilized), allowing soldiers to remain cloaked indefinitely, and easily position themselves to employ "hit and fade" tactics.
      • Mimetic Skin prevents foes from targeting or reacting to a cloaked soldier, allowing a squad of six to plan ambushes without the risk of detection, scout for Meld canisters, spot for Squadsight Snipers, evacuate civilians, heal injuries, and out flank alien groups with ease.
      • Mimetic Skin is not deactivated by use of non-lethal items and abilities (Psi Inspiration).
      • Mimetic Skin, Adaptive Bone Marrow, and Secondary Heart are best applied to Covert Operatives and psionic squad leaders.
    • Having the Mimetic Skin Gene Mod makes it impossible to activate the Ghost ability on the Ghost Armor; as the Ghost Armor's invisibility does not require to end your movement in high cover or for enemies to not have line of sight to the soldier's starting position, Mimetic Skin is a more restrictive invisibility option and can be actively counter-productive on soldiers wearing the Ghost Armor. This is especially problematic if the soldier with Mimetic Skin is pinned by Overwatch or being suppressed and cannot Grapple away.

Gene Mod Priority[]

Not all soldiers are equal; some classes specialize in certain areas. Because of this, certain soldiers enjoy priority over others in receiving modifications since they can make better use of it than others.

The priority system also makes sense given that Meld and cash are often scarce especially in higher difficulties. This guide is not applicable in every possible situation.

Brain Mods
  • Neural Damping: Assault, Heavy, Support ("Low Will" soldiers)
  • Neural Feedback: Psionic / Squad Leader ("High Will" soldiers)
Eye Mods
  • Hyper Reactive Pupils: Assault, Heavy ("Low Aim" soldiers)
  • Depth Perception: Sniper, Support ("High Aim" soldiers)
Chest Mods
  • Adrenal Neurosympathy: Sniper, Heavy, Squad Leader
  • Secondary Heart: Assault, Psionic, Support
Skin Mods
  • Bioelectric Skin: Assault, Support, Squad Leader, Psionic
  • Mimetic Skin: Sniper, Heavy
Leg Mods
  • Muscle Fiber Density: Assault, Sniper, Support, Psionic
  • Adaptive Bone Marrow: Heavy, Squad Leader

Build and Tactics[]

This guide assumes you are already familiar with how the Gene Mods work and how they are obtained.

Psionic Class / Squad Leader[]

  • Secondary Heart, Adaptive Bone Marrow, Neural Feedback: For unrivialed innate survivability: if your Support has Revive then that's a great combo too, since the Psionic can heal up to full base health by himself.
    • The "Psionic" Assault's skills synergizes gives a dramatic boost to his innate survivability. The Assault can make great use of the Adaptive Bone Marrow and Extra Conditioning with the high base health. The Resilience and Secondary Heart prevents sudden spikes in damage from critical hits, and eliminates the will penalty from the critical wounds Assaults tend to receive regularly. Assaults are frequent targets for psi attacks, so Mind Controlled Assaults prove extremely dangerous against allies, since these soldiers often ignore cover in order to deliver lethal point-blank shots; these Mind Controlled Assaults can be downed without concern, then revived afterwards.
    • The "Psionic" Heavy is a frontline soldier easily susceptible to psi attacks. Always boost survivability and keep a brain mod on your Heavy. The Secondary Heart and Adaptive Bone Marrow combo synergizes with Will to Survive and prevents a potentially dangerous situation: Heavies have no pistols to switch to, so Mind Controlled Heavies will attack with high-powered weapons.
    • The "Psionic" Sniper has no use for these mods. They should be far away from the dangers of death and critical injury in the first place. The Secondary Heart is useful only for insurance purposes so that your Mind Controlled "Snap Shot" Sniper does not die a sudden death.
    • The "Psionic" Support has no skills to mitigate damage actually received. The Support is better at healing or preventing damage--rather than dealing or absorbing it--so a Mind Controlled Support is moot.

Assault Class[]

The Assault excels at fighting; whether offensive or defensive. They have several skills you can take to improve their survivability such as Tactical Sense, Lightning Reflexes, Extra Conditioning and Resilience. This means they are more difficult to kill and enjoys the highest priority.

  • Muscle Fiber Density and Mimetic Skin: When combined with Run and Gun, this allows Assaults to remain cloaked indefinitely, roam far from allies when scouting for Squadsight Snipers, safely sneak behind enemy lines to attack flanked foes, and easily position themselves to employ "hit and fade" tactics.
    • WARNING: When Close Combat Specialist activates, Mimetic Skin deactivates, potentially exposing the Assault to certain death - care must be taken to stay farther back from enemies to remain cloaked through the enemies' turn.
  • Hyper Reactive Pupils: When combined with a S.C.O.P.E., this allows Rapid Fire, Close Combat Specialist, and Close and Personal Assaults to benefit from firing twice in a single turn.
  • Adrenal Neurosympathy: Riflemen Assaults perform spectacularly with Combat Rush buff active. The added aim, critical chance and movement from this mod fit their aggresive playstyle perfectly.
  • Bioelectric Skin: Shotgun Assaults benefit from this mod since it's usually them who stack up behind a doorway before breaching a room. Bioelectric Skin can detect the threats and their positions before storming them.

Heavy Class[]

Heavy needs to be at the frontlines. The Heavy has mobility issues: it needs "set-up" before using the Rocket Launcher or Suppression. Survivability is also a concern since the Heavy is often in the firing line.

  • Hyper Reactive Pupils: When combined with a S.C.O.P.E., this allows Bullet Swarm Heavies to benefit from firing twice in a single turn.
  • Mimetic Skin: Heavies need good positioning at all times to find the range for their rockets or to cover the area in Overwatch fire. Mimetic Skin removes that weakness.
  • Bioelectric Skin: When combined with Mayhem, and a Blaster Launcher, a Heavy can kill most enemies without being seen.
  • Adrenal Neurosympathy It's a mixed bag. On the one hand, Anti-Tank Heavies can trigger Combat Rush easily, but firing rockets don't benefit from the aim and critical chance bonuses of Combat Rush. On the other hand, Gunner Heavies may not have the killing power since they're Suppression.

Sniper Class[]

Snipers are the least reliant on gene mods to be effective. They tend to stay far away from the battles. A few key mods will do and even then, there may be ways around their weaknesses (such as S.C.O.P.E.S. or Skeleton/Ghost/Archangel Armor). As such, there's no hurry to modify them.

  • Muscle Fiber Density and Depth Perception: When both are combined with Damn Good Ground and a S.C.O.P.E., this allows Squadsight Snipers to easily reach and fully utilize elevated positions.
  • Mimetic Skin: When combined with Low Profile, the Sniper Major's ability that makes partial cover count as full, Mimetic Skin allows Covert Ops and Snap Shot Snipers to remain cloaked indefinitely, and easily position themselves to employ "hit and fade" tactics.
  • Adrenal Neurosympathy: Snipers are excellent at delivering the coup de grace and can trigger Combat Rush easily enough for your team. (Squadsight Snipers frequently lag behind the rest of the squad.')
  • Bioelectric Skin: Snipers could benefit from the strangled immunity, but Battle Scanner ability may take the place of this gene mod.

Support Class[]

The Support Class is the lowest priority for mods. Their skills (Medkits, Smoke Grenades and Overwatch) are powerful enough on their own and don't synergize as much with gene mods.

  • Hyper Reactive Pupils: When combined with a S.C.O.P.E., Covering Fire, Sentinel, this allows Sentinel Supports to benefit from firing twice in a single turn.
  • Muscle Fiber Density and Mimetic Skin: Allows aggressive height advantage that makes Overwatch shots more accurate. When combined with a Sprinter, this allows Savior Supports to remain cloaked indefinitely, and traverse any terrain to heal injured allies with Medikits, in addition to providing adequate defense with Smoke Grenades.
  • Bioelectric Skin: Bioelectric Skin naturally makes sense since the Support is typically moves with the Squad. Prevents Seekers from getting close as well as free up the Support to help squadmates being strangled.
  • Adrenal Neurosympathy: Getting Combat Rush for your squadmates is great bonus; if you can arrange to get it.


  • If a soldier gets knocked out by Neural Dampening whilst on Overwatch, followed immediately by an enemy crossing their line of sight and triggering a reaction shot, the game will get stuck in the slow-mo animation because the soldier is unconscious and unable to shoot. This will also happen when using Close Combat Specialist. Until this bug is fixed, it would be advisable to avoid putting soldiers with Neural Dampening on Overwatch when engaging Sectoid Commanders or Ethereals.

By hitting Tab repeatedly, you may be able to "slow forward" the situation until the movement has finished. This may require one or two minutes of switching soldiers as the animation is only forwarded one frame per tab-press. After this, the camera is stucked but you can give orders to the other soldiers. After ending this round, all returns back to normal.


  • Genetically modified soldiers receive unique sleeveless armor design types with access to eight different armor deco options specifically just for them.


  • "Mutare Ad Custodiam" is Latin for "Change to Protect".