While working on a mutation table for my Macho Women with Guns game, I created a few more realistic mutations, that could be used for other post-apocalyptic games. As the designers of the Gamma World game could probably tell you, it is a lot easier to create unrealistic mutations than to create realistic mutations.

With that preamble, I present the following somewhat realistic mutations that are not too delibitating but might provide an interesting edge or disadvantage to a PC in even a more serious post-apocalyptic game.

Albino (-4 points)
Your skin is white and sunburns very easily. In an era with depleted ozone, this can be very bad. Depending on current UV levels, an albino’s skin will develop a sunburn after 10-60 minutes of exposure to direct sunlight. This sunburn will get worse with further exposure (see rules to be developed regarding sunburn, under environmental hazards). Albinism usually affects the person’s eyesight, inflicting a penalty of -0 to -3 (roll d4-1 for your character) to any rolls involving eyesight. In addition, albinos have a 85% chance of also having the effects of Light-Sensitivity below.

Colorblind (0 points)
You can not distinguish colors. Roll d6: on a roll of 1-3 you can’t distintinguish red from green; on a roll of 4-5 you can’t distinguish blue from yellow; on a roll of 6 you can only see in shades of grey. This grants a couple of minor advantages despite not being able to tell a red bikini from a green bikini: you gain a +1 bonus to Search and Alertness rolls to see something hidden among colorful camouflage, and an additional +1 bonus to Alertness rolls in the first five minutes after a dramatic drop in illumination. (The latter bonus works to offset any applicable circumstance penalty by 1.)

Cowardice Instinct (-1 point)
You have instincts that protect you from getting hurt. This gives you a +1 dodge bonus to AC, but a -4 penalty to all attack rolls, and a -1 penalty to all damage rolls made with melee weapons.

Fast (2 points)
Your base speed increases by 5 feet.

Firm Grip (1 point)
You have a firm grip. This is normally worth a +1 reaction bonus when you shake hands with somebody, as well as a +2 bonus to Intimidation rolls if you get to show somebody just how strong your grip is. You gain a +1 bonus to grapple, climb, or disarm checks. However you take a -1 Initiative Drop whenever you wish to let go of an object.

Improved Ability (3 points)
You gain 1d6 points in a randomly chosen ability (Strength, Dexterity, Constitution, Intelligence, Wisdom, or Charisma).

Increased Allure (2 points)
You are blessed with an exotic comliness. Roll 1d4 to determine the bonus you gain to any charisma-related checks regarding the opposite sex. You gain double this roll as a permanent bonus to your Presence score.

Instinctual Insight (2 points)
Pick any feat. You gain this feat. If this feat has prerequisites, you may not use it until or unless you meet the prerequisites, but gain the benefits immediately upon meeting these prerequisites. For example, if you choose Improved Critical, you do not gain any advantage until your BAB is +8 or higher, but then immediately gain the advantages of the Improved Critical feat when your BAB reaches this level.

Keen Eyesight (2 points)
You have keen eyesight. This grants a +2 bonus to Alertness checks, or +4 to spot and search checks.

Keen Hearing (2 points)
You have pointed ears that help you hear things. This grants a +2 bonus to Alertness checks, or +4 to listen checks. You can also hear ultrasonic and infrasonic sounds, but need to save against any sonic damage you take (DC equal to the damage taken) to avoid being stunned for one round.

Light Sensitivity (-3 points)
Your eyes are sensitive to light, making it difficult to see in bright daylight. You gain a bonus of +1 to +4 when in low-light conditions, but suffer the same penalty in bright-light conditions. This bonus or penalty applies to any checks involving eyesight.

Lowered Ability (-2 points)
You lost 1d4 points in a randomly chosen ability (Strength, Dexterity, Constitution, Intelligence, Wisdom, Charisma).

Sensitive Skin (0 points)
Your skin is particularly sensitive. This can be both an advantage and a disadvantage. You gain a bonus to Alertness checks of from +0 to +4 based on your state of attire. Unfortunately, any time you take damage, either lethal or nonlethal, you must make a Fortitude Save against the damage you take in order to avoid being stunned for 1 round. You also suffer a distraction penalty of -1 whenever you suffer negative effects due to environmental heat or cold.

Slow (-2 points)
Your base speed is reduced by 5 feet.

Tough Skin (1 point)
Your skin is tough and leathery, granting a +1 natural armor bonus to Defense.

Weak Grip (-2 points)
You have trouble holding on to things. You take a -2 penalty to any grapple, disarm and climb checks. If you roll a natural 20 on an attack roll, you have to make a Fortitude Save against DC 15 to avoid dropping your weapon.
For this list, I tried to think of mutations that would fit in lines with what we currently believe about evolution; small advantages that would be barely noticable in many cases, but might offer a slight advantage in game terms. For Albinism and Colorblindness, I looked those up on Wikipedia and skimmed the articles to decide what the game effects would be.