In the previous post of this series, we figured out that chromosomes carry genes, and we used genetic linkage and crossing over to start making gene maps of chromosomes. Given enough data on offspring and inherited traits, we could continue this project and make ever more accurate gene maps, identifying the components of chromosomes in ever finer detail. In fact, that’s what went on for some time after Sturtevant’s work in 1913. But we know that this can’t be the end of the story. We know what a gene is now, but we still haven’t talked about a genetic code. How do genes even work? In part 1, we introduced the concept that a gene on a chromosome can ultimately, through a chain of biochemical events, lead to someone having blue eyes:
