I'm assuming you're at Customs in the Altair Colony still in the earlier part of the game. As you face all those gates in front of you, only the left-most one will let you through, but you have to repair the base of its desk first (there's a panel down there you open to fix it). Then at the top of the desk, click on the panel to find another pass code panel to enter the DNA code into. The DNA number is from that DNA scanner back on the Ariadne Space Station- 9395. Then walk through that beam, then go further ahead and you should be able to open the gate to pass through.
Hope this helps!