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.该20000至30000基因，现在被认为在人类基因组，大部分细胞表达，只有极少数的一部分-这使得意义上说，肝细胞已很少需要的D NA代码，使神经元。

But as almost all cells carry around a full copy ('distribution') of the genome, a system is needed to #ifdef out stuff not needed.但由于几乎所有的细胞进行左右的完整副本（ '分配' ）的基因组，一个制度是需要＃ ifdef出来的东西并不需要。 And that is just how it works.这是刚才是怎么做到的。 The genetic code is full of #if/#endif statements.遗传密码是充满＃如果/ ＃ endif报表。

This is why 'stem cells' are so hot right now - these cells have the ability to differentiate into everything.这就是为什么'干细胞'这么热的权利，现在-这些细胞有能力分化成的一切。 The code hasn't been #ifdeffed out yet, so to speak.代码并没有被＃ ifdeffed出来，但可以这么说。

Read more阅读更多 here这里 to understand DNA through the eyes of a programmer.要了解的DNA ，通过眼中的程序员。