Day 68 is the most gene-poor of any part of Chromosome 3: only four protein-coding genes (browser view). Two are related: ROBO1 and ROBO2 (roundabout homologs 1 and 2).
Roundabout genes were discovered in fly. The roundabout proteins are on the surface of growing axons in the brain, and help them decide whether to cross between the halves of the brain.
Roundabout genes are found as far away as worm, meaning they are at least 550 million years old.
Click here to see the sequence of Day 68 with ROBO1 underlined.