The Mission Priority: Tuchanka becomes available after Priority: Sur’Kesh and either one of Attican Traverse: Krogan Team, or Tuchanka: Turian Platoon, and revolves around curing the Genophage.
Choice: Curing the Genophage or not
This Mission, takes a lot of your choices from the previous games into consideration. If you kept Wrex alive on Virmire in Mass Effect 1, he’ll play a big part in this mission, same goes for Mordin, providing he survived the Suicide Mission in Mass Effect 2. One of the biggest choices carried over is whether you Kept or Destroyed Maelon’s Data, as destroying the data will make Eve die no matter what. The major choice you’ll have to make is whether to warn Wrex and the Krogan Leaders about the sabotage that the Dalatrass tells you about. This will have a severe outcome depending on your choices.
Warn them of the Sabotage
When given the chance, if you tell the Krogan Leaders about the sabotage, your STG doctor (Mordin, if he survived) will fix the sabotage before dispersing the cure.
Don’t Warn Them - Wrex/Eve Are Alive
Choosing not to warn the Krogan Leaders, and Wrex and/or Eve are alive will result in your STG doctor not knowing that it’s been sabotaged until they’re at the Shroud. This mean you’ll have the choice of letting the doctor go up and disperse the cure or kill them to prevent them doing so.
Don’t Warn Them - Wrex/Eve Are Dead
By not warning the Krogan Leaders with both Wrex and Eve dead will give you the chance to convince the STG Doctor to walk away, providing your reputation is high enough. This is the only option where you can stop the Genophage cure, and have the Doctor come out unscathed.
Outcome of Curing the Genophage or not
By choosing to cure the Genophage, you can gain up to 475 points in War Assets with the Krogans compared to the paltry 150 points in War Assets from the Salarian’s First Fleet.
Curing the Genophage
Curing the Genophage will reward you with The Urdnot Leader, Krogan Clans, and Clan Urdnot as well as some Krogan Mercenaries, if Wrex is the Leader as War Assets. If Wreav ends up as leader, and/or Eve died during the Mission, their strength will be diminished, resulting in fewer War Assets. This choice will also allow you to have an interview with Diane Allers providing you took her aboard the Normandy, the choices with her can reward you with more War Assets. The only Salarian assets you’ll get is the STG force that helped you with the Mission.
Not Curing the Genophage
By not curing the Genophage, Wrex will find out, and confront you during the Mission Priority: The Citadel III, which will lead to his death, this’ll end up diminishing the strength you got for completing the Mission in the first place, if Wreav is the leader, he won’t find out about the deception. However, you will gain the Salarian First Fleet including Mordin if he was spared.