Recombinant DNA technology

Restriction enzymes

The restriction endonucleases and exonucleases (collectively known as restriction enzymes) used in DNA cloning are named after the bacteria they were discovered in, usually followed by a capital letter and/or roman numeral. Use italics for the bacterial abbreviation:

HindIII     EcoRI     SmaI     BamHI

Restriction enzymes are one of type I, type II or type III. Type II enzymes are the most useful in subcloning.

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Vectors (transfer agents) for DNA cloning are most commonly plasmids, phages, cosmids, bacterial artificial chromosomes (BACs), yeast artificial chromosomes (YACs) or mammalian artificial chromosome (MACs).

Commerically available plasmids are denoted by a lower case p, followed by the plasmid name:

pUC18     pBR322

Because many vectors are customised for a particular use, there is no common naming convention for them.

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Genetically modified organisms and products

Use lower case, and add an s to the abbreviation for the plural:

genetically modified organism (GMO)     genetically modified organisms (GMOs)     GM plants     GM products 

Reminder. Just because the abbreviation of a term is made up of capitals, it does not mean that the term has initial capitals when it is spelt out.

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Describing genetic modifications

Use lower case for terms describing either the function or appearance of a genetically modified organism:

insect-resistant corn     golden rice

Use initial capitals for trade names of genetic modifications, but not for the organism that has been modified: 

Roundup Ready corn     GlyTol cotton     Liberty Link rice

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Terms to watch out for:


cloning (general): replicating and propagating the genetic makeup of an organism, either partially or completely. There are several different types of cloning (see below)

clone (cell culture): a population of cells derived from a single cell by cell division (mitosis). The clone is seen as a clump of cells in the cell culture dish. The cells in a cell culture clone are not necessarily identical

clone (plants): may refer to a cultured clone (as above), or to a group of plants derived by propagation from a single individual through cuttings or other asexual means

clone (bacterial): the unicellular progeny of a single bacterial cell. When grown on agar in petri dishes, bacterial clones form clusters (colonies)

molecular or DNA cloning: copying a particular sequence of DNA, and transferring it to a different cell (usually bacterial or yeast) using a DNA vector (usually a plasmid, phage or similar), where it is copied along with the rest of the cell’s DNA when the cells divide. This method can be used to produce large quantities of the product of the DNA sequence (eg to produce insulin). See also Recombinant DNA technology

cloning (animals): a type of reproduction in which the complete genotype of an animal is copied, generally by replacing the nuclear DNA of an egg cell from a host with the nuclear DNA of a body (somatic) cell from the donor organism (a process called somatic cell nuclear transfer). ‘Dolly’ the sheep was created in this way

therapeutic cloning: a method to obtain perfectly matched human embryonic stem cells from an individual. These cells have the potential to become tissue-specific cells that can be transplanted back into the individual to repair damaged cells or tissues without risk of rejection. The technique involves somatic cell nuclear transfer – the same technique that created Dolly the sheep – but the cloned egg cell containing the individual’s DNA is only allowed to form a small cell cluster (blastocyst), the inner layer of which is rich in stem cells. These stem cells are removed and used to create the specific cell type(s) required

See all terms

Many biotechnology methods involve cloning. Cloning refers to replicating and propagating the genomic makeup of an organism, either partially or completely.

There are several different types of cloning, and it is important to be clear about which one you are referring to.

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