把物質（一般是遺傳物質）轉入宿主細胞或生物的運載體。一般而言，載體有兩種類型---病毒或DNA類。DNA載體是可以自我復制的環狀結構，易于攜帶遺傳物質和純化。用一般的實驗室技術將它們轉入細胞體內。這些載體具有不同的特征，包括質粒、粘粒和酵母人工染色體。經過生物工程處理成無害的組合病毒也可攜帶遺傳物質并在實驗室內將其轉入細胞或整個宿主生物體，后者即基因治療的一個例子。

 
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.