把物质（一般是遗传物质）转入宿主细胞或生物的运载体。一般而言，载体有两种类型---病毒或DNA类。DNA载体是可以自我复制的环状结构，易于携带遗传物质和纯化。用一般的实验室技术将它们转入细胞体内。这些载体具有不同的特征，包括质粒、粘粒和酵母人工染色体。经过生物工程处理成无害的组合病毒也可携带遗传物质并在实验室内将其转入细胞或整个宿主生物体，后者即基因治疗的一个例子。

 
A vehicle that transfers material (typically genetic) into a host cell or organism. Typically, vectors are of two types – viral- or DNA-based. DNA vectors are self replicating, circular elements that can be easily manipulated to carry genetic cargo and are easily purified in bulk; they are transferred into cells by standard laboratory techniques. These vectors can have different features (such as the size of DNA-insert they can accommodate) and include plasmids, cosmids, and yeast artificial chromosomes (YACs). Recombinant viruses that have been bioengineered to be harmless can also carry genetic cargo for transfer into cells in the laboratory, or into an entire host organism, the latter is an example of gene therapy.