OSMOSIS 7, AUTUMN 1994
Contents
An Introduction from the Director
Noticeboard
Growing radishes in film cans
DNA and rDNA applications
The Conifer Conservation Programme
Make a portable pond
Introduction from the Director
Dear Colleague,
We have collaborated with Philip Harris on the production of four rapid-cycling brassica (fast plant) kits:
· Basic Kit contains normal (wild-type), high anthocyanin-expressing seed, and everything needed to grow the plants (except lights) including detailed documentation.
· Simple Genetics Kit contains normal wild-type seed, the seed of a mutant called Yellowgreen and F1 seed from a cross between the normal and Yellowgreen mutant. The kit includes the usual equipment and comprehensive documentation.
· Mendel's Second Law Kit contains seed of two mutants: Yellowgreen and Rosette; and enables Mendel's Second Law to be tested. Great opportunities for Science 1 investigations at the highest levels, A-level projects, Advanced GNVQ assignments and CSYS projects, etc. Equipment and full documentation included.
· Variation and Evolution Kit contains normal and Rosette seed together with gibberellic acid and advice on how you can test Lamarck's Hypothesis inside one term!
These kits are available from Philip Harris Education, Lynn Lane, Shenstone, Lichfield, Staffs, WS14 0EE, England. (Tel: 01543 480077; Fax: 01543 480068).
Richard Price
Director
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Noticeboard
Your questions answered.
Q.When the brassica kit, which I ordered from Philip Harris, didn't arrive I telephoned them and was told that they are re-ordering seed.
· Philip Harris have told us that sales of brassica kits and seed are exceeding their expectations - and that this is why you sometimes get this response from them. We are urging them to keep larger stocks. If you get problems of this sort please contace our Cambridge office with full details (e.g. date ordered, etc.) and we shall follow it up on your behalf.
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DNA and rDNA applications
DNA was shown to be the carrier of genetic information in the late 1940s. In 1953, the double helix structure was deduced by Watson and Crick. DNA research continued and, in 1957, Crick published his so-called central dogma which encompassed the three basic reactions involving DNA:
· Replication DNA to DNA
· Transcription DNA to RNA
· Translation RNA to protein
During the late 1960s, a number of DNA modification enzymes were discovered, including the restriction enzymes which cut DNA within or near a four or six base recognition site. This discovery allowed the first recombinant DNA (rDNA) experiments to be performed.
It was not until the 1980s that the commercial potential of the technology was recognised. The molecules which first interested investors were the interferons which are produced during viral infections and have an inhibitory effect on the virus. Resources were invested to analyse the molecules and produce DNA sequences which coded for the interferon protein. Now, a number of interferon molecules can be produced relatively cheaply using bacterial and other cell systems which have had the interferon DNA sequence inserted into them. About 15 therapeutic proteins produced by rDNA methods have, to date, passed the stringent safety rules and are being marketed in Europe and the USA.
The Human Genome Project has the central aim of describing the whole of the 3 billion base pairs in the human genome by the year 2003, the golden anniversary of the description of the double helix structure of DNA. It is hoped that this will lead to a fuller understanding of the biology of man and a better understanding of many of the disorders and diseases that afflict mankind.
Around 1,200 human conditions have been recognised as having a genetic component. In the majority, a complex series of symptoms results from the condition (a syndrome), making study and treatment strategies difficult. DNA technology has allowed novel approaches where the initial effort in the study of a condition is the location of the gene responsible. Extensive DNA analysis eventually locates the gene which can then be cloned into a simple system. The gene's primary protein product can then be synthesised and examined. Possible treatment strategies may then follow.
In 1982, this method was first applied to the search for the cystic fibrosis (CF) gene, one of the most common genetic disorders. In one form of CF a single amino acid is lacking in the protein of affected individuals that regulates the transport of sodium and chloride across cell membranes. Based on DNA sequences, a simple test can be applied to the DNA of individuals to see whether they are carriers of the condition. Trials are also taking place to correct the problem in affected individuals including inhaling the synthesised protein, and introducing the gene into the cells of the lungs in an attempt to give a permanenet cure.
There is now a considerable range of genetic tests available using DNA probes, and as more and more genes are discovered, more complete genetic screening becomes possible. These advances raise difficult ethical issues. For example, should employers and life insurance companies have access to this information?
Since the rediscovery of Mendelian genetics at the start of the 20th century, crop improvement has been possible in a more controlled fashion. However, a consequence of the centuries of selective breeding, based on the strategy of saving seed from the best of the previous generation, was to narrow the genetic base of crop plants. This is likely to be an obstacle to further improvement. Traditional plant breeding is unlikely to be able to keep up with the continued demands for food. Using DNA technology, there are now several strategies available to the plant genetic engineer including the creation of hybrids between unrelated plants by the process of cell fusion. Using this technique gene combinations which are not possible through normal pollination techniques can be generated.
Plants can also be infected with engineered vectors and new genetic material then incorporated into the plant genome. Agrobacterial transformation has been used to incorporate genes for insect resistance into several varieties of plants including potato and tobacco. Viral-resistant crop plants are being developed using part of the pathogenic viral DNA to confer viral resistance on the plant.
By the mid 1990s, around 100 plant varieties had been produced with characters altered by genetic engineering techniques. World-wide there have been trials of many of these plants and some are being used commercially in certain countries. The "flavr savr" tomato is the first engineered plant to receive a full commercial licence in the USA. This tomato has some of its own DNA removed and re-inserted in reverse order such that the enzymes which cause it to soften on ripening are non-functional. The shelf- life is consequently greatly increased.
One argument against weed killer-resistant strains is that the crops themselves might become "superweeds" and would take over natural habitats in the same way as has been the case with the introduction of some exotic weeds in the past (e.g. the prickly pear cactus in Australia). In the case of recombinant crop varieties, this argument claims that control would not be possible because of the genes conferring weedkiller- resistance. A study of the biology of weeds reveals that they have highly specialised characteristics which result in "weediness". It seems unlikely that weedkiller- resistant crop plants, with all of the highly modified characteristics of a crop, would pose any threat as potential "superweeds". There is also the possibility of control by a second weedkiller to which the crop had no resistance.
Most of the scientific community would support regulation and control over the production and release of genetically modified organisms be they micro-organisms, plants or other species. This caution is based on the fact that it is certainly possible to produce organisms harmful to mankind. Regualtion associated with careful control must be the first safeguard against such a situation.
As the science advances, the public debate continues on the ethical and legislative issues and the necessity for a more informed public becomes increasingly urgent. Schools are an obvious place in which literacy of this science could be furthered. A theory-only approach may be counter-productive in generating a positive attitude to DNA science. Practical hands-on work in which real situations can be demonstrated and tested not only increases understanding but stimulates an interest and enthusiasm for the science.
The hands-on workshops for teachers developed by SAPS show how students can carry out exciting practical work on DNA using safe protocols and inexpensive materials (see workshop calendar for details of workshops, or contact our Cambridge office for the name and address of the nearest DNA workshop leader).
Geraldine Russell and Barry Miller
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The Conifer Conservation Programme
The role of botanic gardens has changed since their first development in the mid sixteenth century, when they served as centres for growing and studying medicinal and culinary plants. One modern-day role is conservation. However, because of limited space, it is not easy to grow the numbers of threatened plants that are needed to conserve the broad genetic spectrum.
It has been estimated that, of the world's 662 conifer species, 364 are threatened in their natural habitats. Most are in decline because of the exploits of man: wholesale timber extraction or forest clearance for agricultural use. But some have suffered because of natural phenomena such as fire, flooding and volcanic activity.
In 1991 the Royal Botanic Garden, Edinburgh launched a Conifer Conservation Programme. The aim is to collect seed from across the natural range of each threatened conifer and establish breeding populations of conifers in a network of safe ex situ sites throughout the British Isles. In future years these living gene banks will serve as a vital source of replenishment for depleted wild populations. Already we have visited Spain, Mexico, Chile, Taiwan and N. America in order to collect seed and we now have 52 sites from the Hebrides to Penzance.
The better known threatened conifers include the Cedar of Lebanon, of which there are less than five trees left in Lebanon, and the bulkiest tree in the world, the Giant Redwood, but perhaps the most notable is the Monkey Puzzle. This strange looking conifer, which is native to the Chilean and Argentinean Andes, has hardly changed since dinosaurs roamed the Earth some 70 million years ago. There is no doubt that it's spine-tipped leaves were an excellent defence against these foraging animals. Many of the large Monkey Puzzles seen in parks and gardens today were planted in about 1840 - 1850. However, the first introduction was in 1796 when the Scotsman, Archibald Menzies, who was then attached to Vancouver's voyage of survey, pocketed five seeds from a dessert bowl when attending a banquet as a guest of the Governor of Chile.
Many of the Conifer Programme's safe sites are with private landowners who welcome a tangible link with conservation. Other sites are in publicly accessible areas such as zoos and public parks which are able to use the trees with educational activities for the visiting public - particularly schools.
With the help of two Scottish school teachers the Conifer Conservation Programme has developed an education pack that is relevant to the Scottish curiculum: Data interpretation for revised Higher Biology and A guide to problem solving in biology for Standard Biology. The pack is accompanied by a short introduction to conservation strategies and a small illustrated newspaper called the Conifer Times which highlights a threatened conifer from each continent.
Martin Gardner
Programme Manager Conifer Conservation Programme
The Royal Botanic Garden Edinburgh, Scotland.