Plasmids that are used most commonly in the field of recombinant DNA technology have been optimized for their use of studying and manipulating genes. For instance, most plasmids are replicated in E. coli and are relatively small (∼3000 - 6000 basepairs) to enable easy manipulation. Typically plasmids contain the minimum essential DNA sequences for this purpose, which includes a DNA replication origin, an antibiotic-resistance gene, and a region in which exogenous DNA fragments can be inserted. When a plasmid exists extrachromosomally in E. coli, it is replicated independently and segregated to the resulting daughter cells. These daughter cells contain the same genetic information as the parental cell, and are thus termed clones of the original cell. The plasmid DNA is similarly referred to as cloned DNA, and this process of generating multiple identical copies of a recombinant DNA molecule is known as DNA or molecular cloning. The process of molecular cloning enabled scientists to break chromosomes down to study their genes, marking the birth of molecular genetics.
Below you will find helpful resource tables about the genetic code. This table includes the nucleotide and amino acid code in addition to ambiguous bases and common epitope tags. Ambiguous bases are included in a DNA sequence when sequencing is not 100% efficient and the machine cannot distinguish between the 4 labelled nucleotides. Epitope tags on the other hand are commonly used in molecular cloning to tag a gene within a plasmid.
The theoretical and historical underpinnings of techniques are prominent features of the presentation throughout, information that does much to help trouble-shoot experimental problems. For the fourth edition of this classic work, the content has been entirely recast to include nucleic-acid based methods selected as the most widely used and valuable in molecular and cellular biology laboratories. Core chapters from the third edition have been revised to feature current strategies and approaches to the preparation and cloning of nucleic acids, gene transfer, and expression analysis. 2b1af7f3a8