Expression vectors allow eukaryotic gene products to be detected in prokaryotes. Bacterial expression vecotrs are usually plasmids with strong promoters, ribosome-binding sites, and transcription terminators. Eukaryotic proteins are made by inserting cDNA into an expression vector. Also, antibodies can be used to screen clones from expression-vector cDNA libraries in order to identify unknown genes.
Since prokaryotes may still not be able to produce eukaryotic proteins (due to a glycosylation requirement), some eukaryotic expression vectors have been established.
Yeast and other similar cells are ideal for such a purpose due to the fact that these cells contain all of the enzymes necessary for normal eukaryotic transcription. Furthermore, recombinant DNA molecules are able to be integrated into the genomes of larger, multicellular organisms such as mammals.
A possible result of such an organism would be the production of a transgenic organism--an organism in which a transformed parent (of recombinant DNA molecules) produces the transgenic offspring, carrying integrated foreign DNA from the parent.
Most Molecular biology on plants has been difficult due to the large size of plant genomes. The research on such genomes as of present is due to a plasmid called Ti. The transforming DNA (T-DNA) is first incorporated into E. coli to produce E.coli shuttle vectors. The bacterium then infects a plant, passing on the T-DNA to the plant genome. Although this technique results in the transformation of only one cell, the procedure is still useful due to the ability of plant cells to de-differentiate and re-differentiate into an entirely new plant.