Transgenic Animals
Given the commercial success of transgenic plants, the lack of commercially available transgenic animals is surprising. There are several reasons for this. Many crops had readily identifiable problems (eg. corn and the European corn borer) that could be attacked with single genes (eg. gene that produces a protein that is toxic to the borer). Such simple problems are less common in animal production systems. For example, feed efficiency (the ability of an animal to convert feed into tissue) is tremendously important; if an animal can gain weight with less feed, the producer can reap large savings. Unfortunetely, a number of factors control feed efficiency, and single-gene solutions are unlikely. Increased animal (eg. pig) growth hormone improves feed efficiency but can also seriously affect animal health (eg. abnormal skeleton development).
Read MoreRecombinant Microbes
To date, the use of recombinant microbes in food production and processing has been limited to recombinant microbial enzymes and a recombinant hormone (bovine growth hormone;BGH) to boost milk production. Recombinant chymosin (rennet) is an example of a recombinant enzymes produced by microbes. The bovine chymosin gene was transferred to several fungal species via recombinant DNA technology in the 1980s. Recombinant chymosin is now widely used throughout the world in cheese making. Chymosin increases the rate of curd formation during initial fermentation of milk by lactic acid bacteria. Traditionally, chymosin was obtained from the stomach of slaughtered calves, but the supply from this source is somewhat unstable. In contrast, recombinant chymosin does not have this instability, because it can be produced through growth of recombinant yeasts in large bioreactors (vessels used for large-scale growth of cells).
Transgenic Plants
Breeding is still an effective mechanism for improvement and is frequently used to increase such traits as yield and disease resistance, as well as characteristic important to food processors (eg. sucrose level in potatoes) and nutritionists (eg. levels of ?-carotene in carrots). However, the great disadvantage that breeders face is the lack of control over the gene mixing that occurs during normal sexual reproduction. When a nucleus from a pollen grain fertilizers a nucleus in an ovule all of the chromosomes of the pollen nucleus are mixed with all of the chromosomes of the egg cell in the ovule. In many cases, undesirable traits are passed to the egg cell along with the desirable traits. In the mid-1970s, plant scientists were quick to see the potential of recombinant DNA technology to revolutionize plant breeding.
Read MoreGene Cloning
The major breakthrough in the development of recombinant DNA technology was the ability to clone genes. This refers to the process of isolating a specific gene from an organism’s genome (the entire set of genetic information in an organism). In general terms, genes are usually clone by inserting fragments of a genome into a vector. A vector is an agent that can be used to move DNA segments from an organism to another. Plasmids, small circular double-stranded DNA molecules that are capable of replication within their host cell, are commonly used as vectors. Once a plasmid vector has been inserted into a cell, the cell that contains the desired gene can be located and separated from cells that contain other fragments of DNA.
Read More‘Golden rice’ and its future
Soon after the ‘Starlink’ scandal, Swiss biotechnologists announced the development of ‘golden rice’, a variety of rice that has much higher levels of ?-carotene than normal rice. The human body can use ?-carotene to synthesize vitamin A. Vitamin A deficiency is widespread in the developing world and is the leading cause of non-infectious blindness. The most common reason for this deficiency is overreliance on rice, which is often the only food available to people living in dire poverty and to subsistence farmers in southeast Asia.
It is uncertain how effective golden rice will be in combating vitamin A deficiency, and it is not a permanent solution to global malnutrition, but it will probably lead to improvements in vitamin A nutrition of some of the world’s poor. The biotechnology industry has been quick to capitalize on golden rice, using it as an example of the potential of biotechnology to beneficially affect human society. This use of golden rice as a public relations tool has been widely criticized, especially by the developers of golden rice.
The pathway of development of golden rice has been very different from that of commercial transgenics. Funding for development came from the Swiss government and an American foundation (the Rockfeller Foundation). The developers of golden rice have always been adamant that golden rice seed would be freely available to farmers in the developing world and that they would not seek intellectual property rights for this transgenic plant. In contrast, companies such as Monsanto have successfully obtained patents for their transgenic crops, and patent rights are vigorously defended. A number of high-profile court cases in the US and Canada have demonstrated that the biotechnology industry considers intellectual property of transgenic crops to be essential.
Read MoreGene Therapy
In 1990, researchers first attempted to combat genetic defects by the transfer of human genes. When a hereditary disorder is the result of a single defective gene, an obvious way to cure the disorder is to add a working copy of the gene. This approach is being used in an attempt to combat cystic fibrosis and it offers potential for treating muscular dystrophy and a variety of other disorders.
One of the first successful attempts was the transfer of a gene encoding the enzyme adenosine deaminase into the bone marrow of two girls suffering from a rare blood disorder caused by the lack of this enzyme. However, while many clinical trials are underway, no others have yet proven successful. This extremely promising approached will require a lot of additional effort.
Food Biotechnology; a threat or improvement?
Why is food biotechnology so controversial? Consumers particularly in Europe, Britain and Japan are particularly hostile to transgenic crops. Many consumers and environmental groups believe that these crops are potentially dangerous to humans and the environment and that these risks have been insufficiently assessed. There is also a common perception that food biotechnology is beneficial only to the companies involved in its development, and not to the general public. It is also a favourite target of anti-globalization activitists, who view biotechnology as a means to exploit producers in the developing world.
Public concern about biotechnology increased in the fall of 1999, when large scale contamination of ‘Starlink’ corn was found in taco shells and various other foodstuffs destined for human consumption. This variety of corn contains a gene that produces a protein toxic to the European corn borer, a destructive pest. However, it was never approved for human consumption; prior to the ‘Starlink’ scandal, however, it could be used in animal feed. The reason for this regulatory strategy was a concern that the novel protein had the potential to provoke an allergic response in humans, because it was somewhat resistant to breakdown by digestive enzymes. As a result of this contamination, several companies suffered substantial fiscal damage and public distrust of food biotechnology grew.
Read MoreDNA Sequence Technology
Exciting scientific advances in DNA sequencing technology in recent years have made the DNA sequencing of entire genome practical. Researchers first focused on microorganism with relatively small genomes, on the order of a few million nucleotide base-pairs (Mb). In general, about half of the genes prove to have a known function. What the other half of the genes are doing is a complete mystery.
The first eukaryotic genomes to be sequenced in their entirety were the microbes brewer’s yeast Saccharomyces cerevisiae (13 Mb) and the malarial Plasmodium parasite (30 Mb). The first animal to have its DNA completely read was the nematode C. elegans (100 Mb) in December 1998, followed by the fruit fly Drosophila (120 Mb) and the mouse (300 Mb). The plants Arabidopsis (100 Mb) and rice (430 Mb) were completed in the year 2001.
One of the most surprising results revealed by these genome sequences has been the discovery of just how similar living things are to one another at the genetic level. Forty-two percent of the genes discovered in C. elegans had some sort of match to genes in other organisms only distantly related. Fully 83% of Drosophila genes match those of other species. The matches are not perfect however-the DNA sequences of genes that do the same job have drifted apart over millions of years. But functionality is maintained. For example, when a gene involved in aye development in mice was substituted for its homologue in Drosophila, the flies were born with normal, functional eyes.
Soxhlet Extractor
This method involves bringing a material to be extracted (usually in solid form) into contact with the extraction solvent for a period of time, followed by separation of the solution from the solid debris.
In this method, the material to be extracted is placed in a ‘thimble’ made of cellulose or cloth in a central compartment with a siphoning device and side-arm both connected to a lower compartment. The solvent is placed in a lower compartment and a reflux condenser is attached above the central sample compartment. Each components of the set up is a separate item of glassware which is assembled together with the appropriate contents, to make the complete apparatus.
The solvent in the lower container (usually a round bottom flask) is heated to boiling and the vapour passed through the side-arm up into the reflux condenser. Here the vapour liquefies and drips into the thimble containing the material to be extracted. The warm solvent percolates through the material and the wall of the thimble and the extracts gradually collects in the central compartments. Once the height of the extract reaches the top of the siphon, the entire liquid in the central compartment flows through this and back into the lower solvent container. The process is then repeated.
Electrophoresis
When my wife was doing her final year projects on fish gellatin, I always heard about electrophoresis. Electrophoresis is a method of separating a mixture of substances that carry an electrical charge. Under the influence of an electrical field the constituent molecular species will move at different rates according to their size, shape and total electrical charge. Electrophoresis is used primarily as an analytical method for small samples of mixtures of charged molecules, particularly proteins, peptides and amino acids, rather than as a fractionation procedure. It can be used in a similar way to preparative layer chromatography to separate the components of fairly simple mixtures.
There has been a considerable revival of interest in analytical electrophoresis in recent years due to the introduction of the technique known as capillary zone electrophoresis (CZE). This technique has the advantage over earlier ones since it can be modified to analysed uncharged molecules as well as charged ones. This technique has not yet been adapted for preparative applications.
