Dark Angels - One of the purest gene seeds, high lords of terra dislike using it for some reason.
Emperors Children - Perfect gene seed, every one functioned at peak efficiency, horribly corrupted by the warp after the heresy.
Iron Warriors - Gene seed causes a tendency for suspicion and paranoia in the IW, but makes them highly intelligent with well developed problem solving abilities. Suffered some mutation in the warp.
White Scars - First thought to be stable and possessing no anomalies, it is unknown whether their savagery and thirst for war is a genetic flaw or because of integration of tribesmen from the steppes and their warlike nature.
Space Wolves - Canis helix causes aspirants to mutate into grotesque wolf monsters, only if they are able to overcome this flaw can they be fully indoctrinated into the chapter. Even after joining, some space wolves can still transform in this way.
Imperial Fists- Stable gene seed, lost the use of sus-an membrane and have no betcher's gland, meaning they cannot enter suspended animation or spit acid.
Night Lords - Most stable and least mutated of all the traitor legions, gene seed causes jet black eyes which provide excellent night vision. Night Lords have a tendency for paranoia and self destructive behaviour. A few amongst them suffer painful seizures and experience visions of the future, much like their primarch.
Blood Angels - Gene seed makes marines susceptible to conditions known as the black rage and the red thirst. The black rage causes them to go insane, believing that they are their primarch at the seige of terra, and instilling a portion of his strength to sufferers. The red thirst can cause blood angels to be overcome with the need to rip their enemies limb from bloody limb, sometimes abbandoning advantageous positions to do so.
Iron Hands - Possess a fanatic hatred of weakness/fear of the organic form, which is believed to be inherited genetically. Causes marines to gradually replace their bodies with bionic enhancements.
World Eaters - Have a physical need to kill that drives them into a berserk fury, this is augmented by pyscho-doctrinal lobotomisation.
Ultramarines - Stable and pure gene seed. Genetic standard for space marines.
Death Guard - Gene seed created gaunt, shadow eyed marines in the image of their primarch. Death guard marines were also noted as having a particularly tough constitution. After the infection of nurgle's rot, gene seed became completely contaminated.
Thousand Sons - Prone to both physical and psychic mutations, increased dramatically when began worshipping Tzeentch, Rubic of ahriman fixed that, kinda.
Lunar Wolves/Sons of Horus/Black Legion - Reliably pure up until Davin incident, since then marines display random mutations expected to go all the way down to gene seed level.
Salamanders - Either because of gene seed flaws, high radiation of their home planet, or combination of both, all salamanders have very dark skin and bright, burning eyes. They also have slower reactions than other space marines.
Raven Guard - Accelerated gene harvesting techniques left a great deal of the raven guard's genetic stock irreparably damaged. Most noted flaws are no mucranoid or betcher's gland, which means they are unable to sweat protective chemicals or spit acid, and the mutated melanchromic organ causes the marine's skin to get paler over time.
Alpha Legion - Suffers some mutation, whether purposely induced to incite terror and revulsion can only be guessed.
Word Bearers - Thought to be pure, since discovered that Word Bearers have a tendency for dogged unquestioning belief and stubborness that borders on insanity. These qualities have only been magnified and warped within the eye of terror. Word Bearers have a particular tendancy towards mutation, but these are seen as gifts from the gods and are encouraged.
Hope this helps! Feel free to correct me if I've got any of this wrong.