Genetically modified organism (GMOs) are created when cloned genes are introduced into germ cells.

在真核细胞中，如果被导入的细胞来自另一种生物，形成的转基因植物或动物可以通过常规育种来繁殖。

Because back then cloning a disease gene was a big deal.

Zoghbi：因为那时候克隆疾病基因是一件大事。

Production of protein from a cloned gene in a defined, nonpathogenic organism would circumvent these problems, and so pharmaceutical and biotechnology companies have developed this technology.

起初，在细菌体内生产是唯一可行的办法，并且cDNA因为没有内含子而常常被使用。

Vectors must normally be capable of being replicated and isolated independently of the host's genome, although some are designed to incorporate DNA into the host genome for longer term expression of cloned genes.

载体还包括筛选标记，一种使含有载体的宿主细胞能从未含载体的宿主细胞中被挑选出来的基因，通常通过使（宿主细胞）获得对毒素的抗性，或者使它们能够在特定的生长条件下存活（来实现筛选）。