Expression cloning is a technique in DNA cloning that uses expression vector

Expression vector

An expression vector, otherwise known as an expression construct, is generally a plasmid that is used to introduce a specific gene into a target cell. Once the expression vector is inside the cell, the protein that is encoded by the gene is produced by the cellular-transcription and translation...

s to generate a library of clones, with each clone expressing one protein. This expression library is then screened for the property of interest and clones of interest recovered for further analysis. An example would be using an expression library to isolate genes that could confer antibiotic resistance

Antibiotic resistance

Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

.

Expression vectors

Expression vectors are a specialized type of cloning vector

Cloning vector

A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted. The insertion of the fragment into the cloning vector is carried out by treating the vehicle and the foreign DNA with a restriction enzyme that creates the same overhang, then ligating the fragments...

 in which the transcriptional and translational signals needed for the regulation of the gene of interest are included in the cloning vector. The transcriptional and translational signals may be synthetically created to make the expression of the gene of interest easier to regulate.

Purpose

Usually the ultimate aim of expression cloning is to produce large quantities of specific protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s. To this end, a bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l expression clone may include a ribosome

Ribosome

A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

 binding site

Binding site

In biochemistry, a binding site is a region on a protein, DNA, or RNA to which specific other molecules and ions—in this context collectively called ligands—form a chemical bond...

 (Shine-Dalgarno sequence

Sequence

In mathematics, a sequence is an ordered list of objects . Like a set, it contains members , and the number of terms is called the length of the sequence. Unlike a set, order matters, and exactly the same elements can appear multiple times at different positions in the sequence...

) to enhance translation of the gene of interest's mRNA, a transcription

Transcription (genetics)

Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...

 termination sequence, or, in eukaryotes, specific sequences to promote the post-translational modification

Posttranslational modification

Posttranslational modification is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins....

 of the protein product.

See also

• Molecular cell biology
• genetics
  Genetics
  Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
  
  
• gene expression
  Gene expression
  Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
  
  
• Transcription (genetics)
  Transcription (genetics)
  Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
  
  
• translation
  Translation
  Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. Whereas interpreting undoubtedly antedates writing, translation began only after the appearance of written literature; there exist partial translations of the Sumerian Epic of...
  
  
• λ phage
• pBR322
  PBR322
  pBR322 is a plasmid and was the first widely-used E. coli cloning vectors. Created in 1977, it was named after its Mexican creators, p standing for plasmid, and BR for Bolivar and Rodriguez....