From Creatures Wikia
A gene is sequence of D-DNA that codes for a particular trait - eg the "highlander gene" from Creatures 1, in which creatures could metabolise glucose to give a much higher proportion of glycogen than "nornal", was a mutation in a gene controlling digestive function. Creatures' genomes, can be opened in external programs, which are used to manipulate individual genes. Often a hex editor, or genetics editor with built-in hex support, is used for this purpose. "01 02 1C 00 00 03 03 3A 01 00 11 3B 01 23 38" is a hexadecimal representation of a gene affected with the aforementioned higlander mutation.