Day 257 has 22 protein-coding genes (browser view) including KITLG (KIT ligand).
A mutation near the KITLG gene increases the chance of being blonde by four-fold. It does this by changing the expression of the gene, which is involved in organizing melanocytes.
Click here to see all 8329707 letters of Day 257 with the rs12821256 blonde-hair mutation flashing.