Are there story elements in Mass Effect 3 which are directly influenced by actions in the first game?

Since ME1 never came out on the PS3, the PS3 version of ME2 made up for the inability to import ME1 saves by including an interactive comic DLC (Mass Effect: Genesis) that makes up for the "missing" game by letting you make decisions that will affect the second game.

I assume an imported save from ME2 which had that DLC will take these key decisions effective in the third game as well, but I was wondering - are there are some actions available in the first game which I'm missing out their direct meaningful influence on the third game because I don't have a save with these actions performed? If so, is there a direct gameplay disadvantage (for example, missing characters, galactic readiness, etc).

Solution 1:

You miss out on a few things, I'd only consider the interactions with Wrex as major:

1. BDTS DLC for the first one allows you to have some war assets if you took the paragon path.
2. Conrad Verner needs to have survived in both the first and second to show up as a war asset in the third.
3. You have to have saved the Rachni queen in the first to gain her as an asset in the third. (The fake rachni queen that's subsituted will betray you).
4. You will miss out on Wrex in general as he's now dead.

There are more but most of them are simply war assets etc.

Solution 2:

If you have the interactive comic for ME2 though both the Rachni queen and Wrex can be saved in that and can then be carried over into ME2 and ME3 respectively.