Definition
Recombinant DNA is a molecule DNA molecule which has been modified to include genes from multiple sources, either by recombination genetics or by laboratory techniques. In the laboratory, bacteria can be transformed with recombinant DNA. Genetic recombination occurs during the meiosis in a process known as crossover.
General description
Recombinant DNA in eukaryotes is responsible for increasing genetic diversity. The alleles of genes that were previously linked to a chromosome can be completely redistributed to create new combinations of traits. This process occurs regularly during meiosis to mix and match genes from paternal and maternal sources.
At genetic engineeringscientists use recombinant DNA created in the laboratory or extracted from a organism to add it to the genome of another organism. Due to the universal design of DNA, recombinant DNA does not have to remain in the same organism. species. This means that scientists can easily add genes from one species to bacteria to produce a product.
For example, insulin is regularly produced by recombinant DNA within bacteria. A gen human insulin gene in a plasmidwhich is then introduced into a cell bacterial cell. The bacteria will then use its cellular machinery to produce insulin protein, which can be harvested and distributed to patients.
Examples of recombinant DNA
Meiosis in eukaryotes
Eukaryotic organisms that undergo meiosis in the sexual reproduction must also go through the process of meiosiswhich reduces the genetic material leading to the fertilisation. During meiosis, the chromosomes of eukaryotes are condensed and paired with their chromosome homologue. Each pair of homologous chromosomes represents the same DNA sequence, from different parental origins. When homologues are connected during meiosis, they may exchange similar DNA sequences in the process of crossover.
While each organism has tens of thousands of genes, the number of chromosomes is much smaller. This requires that there be more than one gene per chromosome, usually hundreds. If genetic recombination did not take place, the variety among these genes would be limited.
For example, imagine that there are only two alleles for coat colour in an populationblack and white. There are also two alleles for the colour of eyebrown and blue. If the gene for eye colour and the gene for coat colour exist on the same chromosome, they are calledlinked genes. Without recombinant DNA, an organism could only pass on the combination of alleles that were passed on from its parents.
Insect-resistant crops
Genetic engineering and recombinant DNA are widely used in modern agriculture. For centuries, farmers have been trying to make their crops resistant to both insects and herbicides used on weeds. With the advent of genetic engineering, scientists can identify and segregate genes of interest and place them into crop species.
To increase insect resistance, for example, scientists have placed bacterial genes into the DNA of corn, cotton and other crops. The genes they selected produce the protein Bt. This protein is lethal to insect larvae that eat it. Scientists create recombinant DNA from the genomes of these bacteria. The new DNA is then inserted into the genome of the crop being protected. When the new plants begin to grow, their cells express the bacterial DNA and the Bt protein is produced.
Farmers who do not grow GM crops must spray their crops with pesticides, which are very expensive. Bt-producing crops protect themselves as they grow. This is important, considering that crop-feeding insects cause more than a billion dollars in damage a year. With genetic engineering, this loss could be avoided.
Gene therapy
Sickle cell anaemia is an inherited blood disorder that affects many millions of people worldwide. In fact, the condition has increased in prevalence because in its milder forms it confers resistance to malaria. Like many genetic disorders, there is currently no cure. Patients with sickle cell anaemia must undergo a variety of dangerous procedures to prolong their lives.
However, gene therapy is an emerging medical technique that uses recombinant DNA to restore the function of cells affected by genetic disorders. Sickle cell anaemia was one of the first diseases to be reversed by gene therapy. The Harvard researchers treated mice with sickle cell traits by delivering the DNA for proper blood cell formation through a virus Altered HIV. Because HIV is prone to the immune system, it readily deposits recombinant DNA into stem cells taken from the host.
The same concept has been used in humans as early as 1990, although mass treatments are not yet available. The use of recombinant DNA viruses is a controversial issue, as a virus could reproduce in the environment with unintended consequences. While the full consequences of these actions are unknown, their many benefits continue to pressure policymakers and the public to accept them. With the right guidelines, recombinant DNA technology is sure to revolutionise the world in a positive way.
Recombinant DNA process
Scientists regularly use recombinant DNA to add traits to certain species of bacteria or produce organisms that have additional traits. There is a basic process for introducing recombinant DNA into cells, although the exact method varies depending on the specific organism.
In general, the first part of the process involves creating a plasmid containing the DNA sequence to be added to an organism. The simplest organism for adding recombinant DNA is bacteria. Bacterial cells reproduce rapidly, allowing many possibilities for recombinant DNA to enter a cell and proliferate.
After creating a plasmid containing the recombinant DNA, it must be added to the cells. To do this, cells are commonly heated to the point where their cell membranes become more permeable. Some cells will die, but the plasmid will successfully make its way into some of the bacterial cells present.
The final process of creating organisms with recombinant DNA is to allow the cells to cool and grow. Often, the introduced plasmid also has a gene that allows the bacteria to survive antibiotic treatment. When the transformed bacteria are grown, an antibiotic is introduced. Any bacteria that survive are those that have been transformed with recombinant DNA. They now have the plasmid, which includes both the recombinant DNA and a gene for antibiotic resistance.
Uses of recombinant DNA
Scientists can use this feature of DNA for many purposes. First, any gene of interest can be easily replicated by inserting the gene into a plasmid and allowing the bacteria to reproduce normally. Plasmids are small rings of DNA. If the exact sequence of the plasmid is known, a scientist can open up the ring using special proteins called restriction enzymes.
Once the plasmid is opened, the chosen gene can be inserted. If all the correct sequences are present, bacteria that take up the plasmid will produce the protein encoded by the recombinant DNA. In addition, when the bacteria reproduce, the gene will also reproduce. Bacteria can double their population in less than an hour, which can lead to large bacterial populations producing large quantities of a product for scientific, medical or industrial purposes.