Derives from the Ancient Greek words of βίος romanized

Biotechnology
Main article: Biotechnology

Construction of recombinant DNA, in which a foreign DNA fragment is inserted into a plasmid vector

Biotechnology is the use of cells or organisms to develop products for humans.^[99] One commonly used technology with wide applications is the creation of recombinant DNA, which is a DNA molecule assembled from two or more sources in a laboratory. Before the advent of polymerase chain reaction, biologists would manipulate DNA by cutting it into smaller fragments using restriction enzymes. They would then purify and analyze the fragments using gel electrophoresis and then later recombine the fragments into a novel DNA sequence using DNA ligase.^[99] The recombinant DNA is then cloned by inserting it into a host cell, a process known as transformation if the host cells were bacteria such as E. coli, or transfection if the host cells were eukaryotic cells like yeast, plant, or animal cells. Once the host cell or organism has received and integrated the recombinant DNA, it is described as transgenic.^[99]
A recombinant DNA can be inserted in one of two ways. A common method is to simply insert the DNA into a host chromosome, with the site of insertion being random.^[99] Another approach would be to insert the recombinant DNA as part of another DNA sequence called a vector, which then integrates into the host chromosome or has its own origin of DNA replication, thereby allowing to replicate independently of the host chromosome.^[99] Plasmids from bacterial cells such as E. coli are typically used as vectors due to their relatively small size (e.g. 2000–6000 base pairs in E. coli), presence of restriction enzymes, genes that are resistant to antibiotics, and the presence of an origin of replication.^[99] A gene coding for a selectable marker such as antibiotic resistance is also incorporated into the vector.^[99] Inclusion of this market allows for the selection of only those host cells that contained the recombinant DNA while discarding those that do not.^[99] Moreover, the marker also serves as a reporter gene that once expressed, can be easily detected and measured.^[99]
Once the recombinant DNA is inside individual bacterial cells, those cells are then plated and allowed to grow into a colony that contains millions of transgenic cells that carry the same recombinant DNA.^[100] These transgenic cells then produce large quantities of the transgene product such as human insulin, which was the first medicine to be made using recombinant DNA technology.^[99]
One of the goals of molecular cloning is to identify the function of specific DNA sequences and the proteins they encode.^[99] For a specific DNA sequence to be studied and manipulated, millions of copies of DNA fragments containing that DNA sequence need to be made.^[99] This involves breaking down an intact genome, which is much too large to be introduced into a host cell, into smaller DNA fragments. Although no longer intact, the collection of these DNA fragments still make up an organism's genome, with the collection itself being referred to as a genomic library, due to the ability to search and retrieve specific DNA fragments for further study, analogous to the process of retrieving a book from a regular library.^[99] DNA fragments can be obtained using restriction enzymes and other processes such as mechanical shearing. Each obtained fragment is then inserted into a vector that is taken up by a bacterial host cell. The host cell is then allowed to proliferate on a selective medium (e.g., antibiotic resistance), which produces a colony of these recombinant cells, each of which contains many copies of the same DNA fragment.^[99] These colonies can be grown by spreading them over a solid medium in Petri dishes, which are incubated at a suitable temperature. One dish alone can hold thousands of bacterial colonies, which can be easily screened for a specific DNA sequence.^[99] The sequence can be identified by first duplicating a Petri dish with bacterial colonies and then exposing the DNA of the duplicated colonies for hybridization, which involves labeling them with complementary radioactive or fluorescent nucleotides.