Protein coding genes, expression prokaryotes

If the end goal of cloning is to have a cloned gene expressed in a cell, the entire coding sequence must be doned intact. Furthermore, if a cloned eukaryotic gene is to be expressed in bacteria (to make recombinant proteins), the gene must not contain introns, which could not be processed in a prokaryotic cell. In these cases it is more convenient to done cDNA rather than DNA restriction fragments. 

The structure and expression of a typical prokaryotic gene coding for a protein is illustrated in... 

Controlled expression of genes coding for biologically active proteins in prokaryotes and eukaryotes, including transformed mammahan cells... 

Controlled expression of gene coding biologically active proteins in prokaryots and eukaryots including transformed mcunmal cells, hybridoma and monoclonal antibody methods. 

A transcription unit represents the combination of regulatory and coding DNA sequences that together make up an expressible unit, whose expression leads to synthesis of a gene product that often is a protein but also may be an RNA molecule. In prokaryotes, proteins in a specific metabolic pathway are often encoded by genes that are clustered and transcribed into one polycistronic mRNA. A polycistronic mRNA encodes for multiple proteins. In such mRNAs, ribosomes are recruited to internal translational initiation sites through an interaction between the 16S ribosomal RNA and the so-called Shine-Delgamo sequence located immediately upstream of the translational start codon that is used to initiate protein synthesis. 

---