The paradox of genetics is that we are very different but actually genetically the same.
All humans share 99.9% of their DNA, but no two people are exactly alike.
There are three or four million differences between my DNA and yours, a tiny fraction of the total, but enough to make a huge difference.
You also have about a hundred personal genetic mutations that are unique to you — that is, none of them match the genes your parents gave you, but are unique to you.
The details of how all this works remain a mystery to us.
Only 2 percent of the human genome is responsible for coding proteins, which means that only 2 percent of the genome is doing anything that makes sense.
What the rest of the genes do, we don’t know.
Lots of genes, it seems, are like freckles on the skin. They’re there, but they don’t do much. There are also some genes that have left people scratching their heads. A particular short sequence of “Alu elements” is repeated more than a million times throughout the genome, sometimes in important protein-coding genes.
It’s a completely meaningless existence by any account, but it still makes up 10 percent of all our genetic material. This mysterious part was once called junk DNA, but now it has a more elegant name — “dark DNA,” meaning we don’t know what it does or why it’s there. Some dark DNA is involved in gene modulation, but much of the rest remains to be determined.