In addition to the Assets and Complications provided in the Cortex Rulebook, the Mass Effect RPG uses an additional set of Traits for your characters. Some are required by race; they are listed on that race's own page as well as mentioned here.
This Asset allows your character to learn biotic talents. It also automatically grants d2 Biotics skill for free. Your Biotics skill is linked to the Biotic asset - that is, your skill cannot go higher than your trait die, e.g. a d8 Biotic trait allows for up to d8 in the Biotics skill tree. At a d12 trait die, d12 and higher (d12+d2, d12+d4, etc.) are unlocked for the skill.
Asari are natural biotics. They start with free d6 in the Biotics skill.
Batarians can take any level of biotics with no ill effects.
Humans can take biotics up to d8. This allows them to specialize and gain access to higher biotic talents without running into adverse effects. If they wish to go higher than d8, they automatically gain the Complication Illness (d4). It can be assumed that they are L2 biotics - stronger implant, but more prone to migranes.
Required for all krogan; not available to any other race. Though it is not foremost on the mind of every krogan, the species is slowly dying out. If you are a fertile female, you are not adventuring. Period. You are mating to let the species live just a bit longer. Otherwise, you act with the sort of reckless abandon of a terminally ill person, knowing that your species is going to die anyway. This is primarily a roleplaying Trait.