An expression vector has all the necessary transcription and translation start and stop signals, along with useful restriction endonuclease cleavage sites nearby, allowing foreign DNA fragments to be inserted in the proper orientation for immediate production of the gene product.
Expression vectors are designed specifically for the expression of a gene of interest. They typically contain promoter regions that initiate transcription, ribosome-binding sites that facilitate translation, and transcriptional terminator sequences that signal the end of transcription. Additionally, they often feature useful restriction endonuclease cleavage sites that allow for the insertion of foreign DNA fragments in a controlled manner.
Option A, shuttle vector, refers to a type of vector that can replicate in different host organisms, typically both prokaryotic and eukaryotic cells. Shuttle vectors enable the transfer of DNA between different species or cell types.
Option B, chimeric vector, refers to a vector that is constructed by combining genetic elements from different sources. Chimeric vectors can incorporate elements from various organisms to achieve specific functions or properties.
Option D, phage vector, refers to a vector derived from bacteriophage (a virus that infects bacteria). Phage vectors are specifically designed to propagate within bacterial hosts, often used for cloning and manipulating DNA sequences.
Therefore, the most appropriate answer is C. Expression.