Deciphering the human genetic code has unraveled several myths.
Do you remember June 26, 2000? Well, it was a historic day, but probably not one to which many people paid attention. US President Bill Clinton invited the head scientists at the Human Genome Project to the White House to publicly announce that the entire human genome had been deciphered for the first time.
Naturally, this feat was groundbreaking. The Human Genome Project was one of the largest scientific enterprises ever attempted; in just eight years it had successfully read the three billion letters of DNA that compose the human genetic code.
What did all this work reveal?
Well, three discoveries stood out. First, humans have far fewer genes than was previously hypothesized. Prior to this decoding, most scientists had assumed that the human genome would contain something like 100,000 genes or even more. The real number is closer to 20,000. Shockingly, roundworms and bananas have more individual genes than people do.
The second surprise was that most of this DNA has little or no function. In other words, readable genes only compose about two percent of the human genome. The rest is entirely incomprehensible. This letter salad is known as “junk DNA,” but it’s not yet clear whether it’s entirely useless.
And finally, the project uncovered one more major insight: the complex nature by which genes interact. For instance, humans have long believed that specific genes code for specific outcomes, say certain types of cancer. But that’s simply not the case.
To prove it, Genome-Wide Association Studies, or GWAS, analyzed the genomes of thousands of individuals with identical medical conditions. Rather than identifying single genes as the cause of their ailments, these studies found tens to hundreds of genes that play a role in any given medical condition.