The following system converts the D20 Future mutation rules to 5th edition D&D. This system can be used for race-building, with 1 MP being roughly equivalent to a +1 ability score increase. If humans exist in your campaign as a baseline race, then balanced non-human races will have a total of 6 MP of abilities.

Mutation Types
Cosmetic Mutations: The simplest and least mechanically complicated mutation is a cosmetic mutation. A cosmetic mutation has no game effect other than to change a creature’s appearance in some fashion. Cosmetic mutations cost 0 MP and impose a -1 penalty to checks to disguise the mutation.
Minor Mutations: A minor mutation not only changes a creature’s appearance in some fashion but also grants it a beneficial (if minor) special ability or useful feature, such as darkvision or gills. A minor mutation costs 1–3 MP, can usually be offset by a single drawback, and imposes a -2 penalty to checks to disguise the mutation.
Major Mutations: A major mutation fundamentally changes the genetics and physiology of a particular creature. Moreover, it grants the creature a beneficial special ability or feature it couldn’t otherwise possess, such as telekinesis or the ability to fly. A major mutation costs 4 or more MP, must be offset by one or more drawbacks, and imposes a -2 penalty to checks to disguise the mutation.
Drawbacks: A creature with minor or major mutations also has drawbacks to offset them. Drawbacks are special disabilities or vulnerabilities that negatively affect a creature. Each drawback has an MP value, and a creature can spend these MP on minor and major mutations to offset the negative effects of the drawback.

Mutations
d%      Mutation Type                   MP Cost  Effect
1–2     Extra Digits [Cosmetic]         0        You have an extra digit on each hand or foot.
3–4     Fins [Cosmetic]                 0        You have fishlike fins on parts of your body.
5–6     Forked Tongue [Cosmetic]        0        You have a forked tongue, which may be longer or oddly colored.
7–8     Horns [Cosmetic]                0        You have tiny horns on parts of your body.
9–10    Scaly Skin [Cosmetic]           0        You have scales covering some of all of your body.
11–12   Thin Fur Coat [Cosmetic]        0        You have a thin coat of fur.
13–14   Unnatural Eyes [Cosmetic]       0        Your eyes are unnaturally colored and/or shaped.
15–16   Unnatural Hair [Cosmetic]       0        Your hair is unnaturally colored.
17–18   Unnatural Skin [Cosmetic]       0        Your skin is unnaturally colored and/or textured.
19–20   Unnatural Voice [Cosmetic]      0        Your voice sounds unnatural in some way.
21–22   Acidic Saliva [Minor]           1        Your bite attack deals an extra 1d4 points of acid damage on a successful hit. You must have a natural bite attack to take this mutation. You cannot gain this mutation if you have the Venomous Bite mutation.
23–24   Adrenaline Jolt [Minor]         3        As a bonus action you can temporarily increase either your Strength or your Dexterity by 1d4+1 points. The increase lasts for a number of rounds equal to 3 + your Constitution modifier. Once you use this ability you cannot use it again until you take a long rest.
25–26   Claws [Minor]                   1        Your hands are claws, which are treated as a pair of simple light finesse melee weapons dealing 1d6 slashing damage.
27–28   Darkvision [Minor]              3        You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.
29–33   Energy Diffusion [Minor]        2        You gain resistance to one of the following types of energy: acid, cold, fire, lightning, or thunder.
31–32   Fangs [Minor]                   1        You have a bite attack which is treated as a simple two-handed finesse melee weapon dealing 1d8 piercing damage.
33–34   Force Barrier [Minor]           3        As a bonus action you can surround yourself with an invisible force barrier, reducing all slashing, piercing, bludgeoning, and force damage you take by 3. This effect lasts for a number of rounds equal to your Constitution modifier (minimum 1 round). Once you use this ability you cannot use it again until you take a short rest.
35–36   Gills [Minor]                   2        You can breathe both air and water. You can operate underwater indefinitely, with no fear of drowning.
37–38   Great Horns [Minor]             1        You have a gore attack which is treated as a simple two-handed melee weapon dealing 2d6 damage (1d10 if your are Small). When you gain this mutation, you choose whether your horns deal bludgeoning or piercing damage.
39–40   Hypersensitivity [Minor]        3        You have advantage on all Wisdom (Perception) checks. You do not suffer disadvantage on attack rolls while blinded.
41–42   Leaper [Minor]                  1        Your jumping distance is doubled.
43–44   Scaly Armor [Minor]             3        You have a +1 natural armor bonus to AC. You cannot gain this mutation if you have fur, chitin, or the Exoskeleton mutation.
45–46   Scent [Minor]                   2        You have advantage on Wisdom (Perception) checks that rely on smell. You can instantly recognize and pinpoint any familiar or unfamiliar smell originating within 5 feet of you.
47–48   Second Wind [Minor]             2        As a bonus action you can regain 1 hit point per level. Once you use this ability you must finish a long rest before you can use it again.
49–50   Smokescreen [Minor]             1        As a bonus action you can produce a 20-foot-radius cloud of smoke centered on yourself. Creatures 5 feet away are lightly obscured, and creatures farther than that are heavily obscured. This ability functions underwater. A moderate wind or current disperses the cloud in 4 rounds. A strong wind or current disperses the cloud in 1 round. Once you use this ability you must finish a long rest before you can use it again.
51–52   Tail [Minor]                    1        You have a tail, granting proficiency in the Dexterity (Acrobatics) skill. You can attack with your tail as simple finesse melee weapon, dealing 1d4 bludgeoning damage. You cannot gain this mutation if you have the Prehensile Tail mutation.
53–54   Thick Fur Coat [Minor]          1        You have advantage on saving throws against the effects of extremely cold climates.
55–56   Ultra Immune System [Minor]     2        You have advantage on saving throws against poison and disease.
57–58   Wall Crawler [Minor]            2        You have a climb speed equal to your base walking speed. You can climb perfectly smooth, flat, vertical surfaces without any trouble.
59–60   Webbed Digits [Minor]           1        You have a swim speed equal to your base walking speed. This does not interfere with your ability to grasp or manipulate objects.
61–62   Echolocator [Major]             5        You have blindsight out to 60 feet, allowing you to perceive your surroundings without relying on sight.
63–64   Elasticity [Major]              5        You have advantage on Dexterity checks to escape a grapple or bonds. You can squeeze through an opening or passage one-tenth the dimensions of your height, moving at one-quarter normal speed.
65–66   Energy Absorption [Major]       4        You gain resistance to two, or immunity to one, of the following types of energy: acid, cold, fire, lightning, or thunder.
67–68   Enlarged Form [Major]           6        You are treated as being one size category larger for attacks and effects whenever it would be advantageous to you. If you are Small you can wield weapons as though you were Medium. If you are Medium you can wield versatile weapons one-handed at their full damage, wield two-handed melee weapons one-handed, and when you wield any heavy weapon in both hands it deals one additional damage die.
69–70   Exoskeleton [Major]             5        You gain a +2 natural armor bonus to AC. You cannot gain this mutation if you have fur, scales, or the Scaly Armor mutation.
71–72   Extra Arms [Major]              6        You grow two additional arms, granting advantage on Strength (Athletics) checks to climb or perform feats of strength. Creatures attempting to escape a grapple with you suffer disadvantage. You can use your extra arms to make two bonus attacks with light weapons or claw mutations (if you have any), but you do not add your Strength or Dexterity modifier to the bonus attacks' damage rolls, unless it is negative. You cannot apply two-weapon fighting benefits to these bonus attacks.
73–74   Gazing Eye [Major]              4        You have an extra eye, which grants proficiency in the Wisdom (Perception) skill. As a bonus action you can use the extra eye to unnerve one creature within 20 feet who can see you. The creature must make a Charisma saving throw (DC 8 + proficiency bonus + 1/2 Charisma modifier). On a failed save the target suffers disadvantage on all saving throws and ability checks for one minute. Any creature that successfully saves against your gaze attack cannot be affected again for 24 hours.
75–76   Pheromone Attraction [Major]    6        You have advantage on Charisma (Persuasion) and Wisdom (Animal Handling) checks made against creatures within 30 feet of you. You cannot take this mutation if you have the Pheromone Repulsion mutation.
77–78   Prehensile Tail [Major]         4        You have a dexterous tail, granting proficiency in the Dexterity (Acrobatics) skill. Your tail is strong enough to support your weight and can grasp and manipulate simple objects up to one size category smaller than you, but it can't do anything that requires opposable digits or fine motor control.
79–80   Prickly Pear [Major]            4        As a bonus action you can deal 1d4 points of piercing damage to any creature you are grappling or any creature that grapples you. You can also damage any creature that swallows you.
81–82   Radioactive [Major]             5        As a bonus action you may release a burst of harmful radiant energy. All creatures within 60 feet of you must make a Fortitude saving throw (DC 8 + proficiency bonus + Constitution modifier) or be permanently poisoned. Once you use this ability you cannot use it again until you take a long rest.
83–84   Skeletal Reinforcement [Major]  5        Add your level to your maximum hit points. Whenever you take damage from falling, reduce the damage taken by one die. You cannot take this mutation if you have the Brittle Bones drawback.
85–86   Stinger [Major]                 4        You have a stinger attack which is treated as a simple light one-handed finesse melee weapon dealing 1d6 poison damage. After performing an attack action you can make a bonus attack with your stinger, but you do not add your Strength or Dexterity modifier to the bonus attack's damage roll, unless it is negative.
87–88   Telekinetic Mind [Major]        5        You can telekinetically manipulate objects, as the mage hand cantrip. Using and concentrating on this ability is a bonus action.
89–90   Telepathy [Major]               5        You can open a telepathic link with a willing, living, and sentient creature within 100 feet. You can communicate telepathically through the link even if you do not share a common language, but no special control or influence is established as a result of the link. If you and the linked creature move more than 100 feet apart, the telepathic link severs instantly. You can telepathically link with only one creature at a time, but you can use the ability at will.
91–92   Tentacle [Major]                6        You have a tentacle growing from your side or back. Creatures attempting to escape a grapple with you suffer disadvantage. Your tentacle is strong enough to support your weight and can grasp and manipulate simple objects of your size category or smaller, but it can't do anything that requires opposable digits or fine motor control. Your tentacle isn’t dexterous enough to fire or throw weapons, but it can be used to make a slam attack as a simple two-handed melee reach weapon dealing 1d10 bludgeoning damage (1d8 if you are Small-sized).
93–94   Venomous Bite [Major]           4        Any creature you successfully hit with your bite must make a Constitution saving throw (DC 8 + proficiency bonus + Constitution modifier) or be poisoned until they take a short rest. You must have a bite attack to gain the benefit of this mutation. You cannot take this mutation if you have the Acidic Saliva mutation.
95–96   Vexing Voice [Major]            4        As a bonus action you can use your voice to frustrate one living creature within 30 feet that can hear you. The creature must make a Wisdom saving throw (DC 8 + proficiency bonus + Charisma modifier). On a failed save the target is incapacitated for one round. Once you use this ability you cannot use it again until you take a short rest.
97–98   Wings [Major]                   6        You have a fly speed of 60 feet.
99–100  X-Ray Vision [Major]            6        You can see through 1 foot of brick or stone, 1 inch of metal or composite alloy, and up to 3 feet of wood, plaster, or dirt. Thicker substances or a thin sheet of lead blocks your vision. X-ray vision has a maximum range of 20 feet and allows you to see as if you were looking at something in normal light, even if there is no illumination.

Drawbacks
d%      Drawback Type               MP Value  Effect
01–05   Ability Decay               4         One of your ability scores (your choice) permanently decreases by 2. You cannot apply this drawback to an ability score of 3 or less. You may take this drawback multiple times.
06–10   Blood Hunger                1         If you go 24 hours without draining a pint of blood from a living creature, your Constitution score is reduced by 1d4. When your Constitution score reaches 0 you die of starvation. Draining blood is an action which only works on a willing or dying (but not dead) creature. The bitten creature takes normal bite damage plus an extra 1d6 points of damage from the blood loss. Drinking a pint of blood restores your Constitution score in 1d6 rounds. You must have a natural bite attack to take this drawback.
11–15   Brittle Bones               4         Subtract your level from your maximum hit points. Whenever you take damage from falling you take an additional 1d6 damage. You cannot take this drawback if you have the Skeletal Reinforcement mutation.
16–20   Combat Fear                 4         Whenever initiative is rolled for combat, make a DC 15 Wisdom saving throw afterwards. If you fail you suffer disadvantage on all saving throws, ability checks, and skill checks for the rest of the encounter.
21–25   Positive Energy Dependency  6         You cannot regain hit points from a long rest. You cannot regain Hit Dice from a long rest unless you receive a cure wounds spell while at full hit points at the start the long rest. Items that would normally provide continuous healing, such as a ring of regeneration, heal you at half the normal rate.
26–30   Festering Sores             2         Whenever you wear any type of armor you do not add your Dexterity bonus to your Armor Class and you have disadvantage on all Strength and Dexterity checks.
31–35   Frailty                     3         You have disadvantage on all Constitution saving throws and death saving throws. You cannot take this drawback if you have the Weak Immune System mutation.
36–40   Heat/Cold Susceptibility    1         You succumb twice as quickly to exhaustion from prolonged exposure to hot and cold climates.
41–45   Lethargy                    2         You have disadvantage on all Dexterity saving throws.
46–50   Light Sensitivity           1         While in sunlight you have disadvantage on attack rolls, as well as Wisdom (Perception) checks that rely on sight.
51–55   Lost Arm                    3         You lose one arm of your choice. You cannot effectively wield weapons that require two hands. In addition, you suffer disadvantage on any skill and ability checks that rely on having two hand, such as climbing, swimming, and grapple checks.
56–60   Mindslave                   2         You have disadvantage on all Intelligence, Wisdom, and Charisma saving throws.
61–65   Alkaline Blood              5         If you go 24 hours without injecting a vial of acid into your veins, your Strength and Constitution scores are reduced by 1. When your Constitution score reaches 0 you die, leaving a petrified corpse. Taking the acid restores your Strength and Constitution scores in 1d6 rounds.
66–70   Pheromone Repulsion         1         You have disadvantage on Charisma (Persuasion) and Wisdom (Animal Handling) checks made against creatures within 30 feet of you. You cannot take this drawback if you have the Pheromone Attraction mutation.
71–75   Poisonous Blood             6         If you go 24 hours without taking a dose of antitoxin, you become poisoned and take 1 point of poison damage per level which cannot be healed by any means. When the poison damage reduces you to 0 hit points you die. Taking the antitoxin removes the poisoned condition in 1d6 rounds.
76–80   Rapid Aging                 1         You age twice as fast as normal.
81–85   Reduced Speed               3         Reduce your movement speed by 5 feet. This speed decrease also applies to any natural burrow, climb, fly, or swim speed you might have. You may take this drawback multiple times.
86–90   Thin Skin                   5         You take 1 additional point of damage each time you are wounded.
91–95   Ultraviolet Allergy         3         Direct sunlight burns you for 2d6 points of fire damage per round and causes any light, flammable clothing you are wearing to ignite.
96–100  Weak Immune System          1         You have disadvantage on saving throws against poison and disease. You cannot take this drawback if you have the Frailty mutation.