Of the 20,000 to 30,000 genes now thought to be in the human genome, most cells express only a very small part - which makes sense, a liver cell has little need for the DNA code that makes neurons.該20000至30000基因，現在被認為在人類基因組，大部分細胞表達，只有極少數的一部分-這使得意義上說，肝細胞已很少需要的D NA代碼，使神經元。

But as almost all cells carry around a full copy ('distribution') of the genome, a system is needed to #ifdef out stuff not needed.但由於幾乎所有的細胞進行左右的完整副本（ '分配' ）的基因組，一個制度是需要＃ ifdef出來的東西並不需要。 And that is just how it works.這是剛才是怎麼做到的。 The genetic code is full of #if/#endif statements.遺傳密碼是充滿＃如果/ ＃ endif報表。

This is why 'stem cells' are so hot right now - these cells have the ability to differentiate into everything.這就是為什麼'幹細胞'這麼熱的權利，現在-這些細胞有能力分化成的一切。 The code hasn't been #ifdeffed out yet, so to speak.代碼並沒有被＃ ifdeffed出來，但可以這麼說。

Read more閱讀更多 here這裡 to understand DNA through the eyes of a programmer.要了解的DNA ，通過眼中的程序員。