The present invention relates to linear expression elements (LEEs) and circular expression elements (CEEs), which are useful in a variety of molecular biology protocols. Specifically, the invention relates to the use of LEEs and CEEs to screen for gene function, biological effects of gene function, antigens, and promoter function. The invention also provides methods of producing proteins, antibodies, antigens, and vaccines. Also, the invention relates to methods of making LEEs and CEEs, and LEEs and CEEs produced by such methods.