• Genetic Recombination and its Application • Recombinant DNA Technology

Genetic Recombination

Genetic recombination is the production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be passed on from the parents to the offspring. Most recombination is naturally occurring. Recombination can be artificially induced in laboratory (in vitro) settings, producing recombinant DNA for purposes including vaccine development.

Applications of Genetic Recombination

1. Vaccine production: Recombinant hepatitis B vaccine: hepatitis B vaccine contains a form of the hepatitis B virus surface antigen that is produced in yeast cells.
2. Diagnosis of infection:  Each of the three widely used methods for diagnosing HIV infection has been developed using recombinant DNA.
3. Herbicide-resistant crops: Commercial varieties of important agricultural crops eg soy, maize/corn, sorghum, are developed with resistance to the herbicide 
4. Insect-resistant crops: Bacillus thuringeiensis is a bacterium that naturally produces a protein (Bt toxin) with insecticidal properties.
5. Recently, plants have been developed that express a recombinant form of the bacterial protein, which may effectively control some insect predators.

Recombinant DNA differs from genetic recombination in that the former results from artificial methods in the test tube while the latter is a normal biological process that results in the remixing of existing DNA sequences in essentially all organisms. Recombinant DNA, rDNA, molecules are formed by laboratory methods of genetic recombination to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in the genome. Recombinant DNA technology is the joining together of DNA molecules from two different species that are inserted into a host organism to produce genetic combinations required.

 Operons

Operons are a set of metabolic genes found only in prokaryotes e.g E. coli. Operons consist of the following:

• Several structural genes
• One promoter and one terminator
• A control site (operator)
• A separate regulator gene (codes for protein that binds to operator)

The Lac Operon

When Lactose is absent

• A repressor protein is continuously synthesised. It sits on a sequence of DNA just in front of the lac operon, the Operator site
•  The repressor protein blocks the Promoter site where the RNA polymerase settles before it starts transcribing

Types of Operons

There are many types of Operons which are being studied.

• The three major ones are:
• Lactose operon (lac operon)
• Tryptophan operon (trp operon)
• Arabinose operon (ara operon).