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10 Risk assessment exercise

After reading this unit you might like to carry out a risk assessment of your office environment or a nearby office and one of the following:

  1. a display-screen user risk assessment;

  2. a laboratory-based risk assessment;

  3. a field-work risk assessment for a proposed field expedition.


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7.3 Disposal requirements

Figure 9
Figure 9 Disposal canister

When carrying out a risk assessment, you must consider disposal requirements. For example, any chemical d
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4.2 The science behind Golden Rice

Modifying crops to produce the Bt toxin (Section 3.1) was, in some ways, relatively simple. The toxin is a single protein and can therefore be produced as a result of the insertion of a single gene into the plant's genome. Similarly, introducing herbicide tolerance (Section 3.2) typically involves modifying the action of a single enzyme, and therefore modification again involves the insertion of a single gene.

β-carotene is not a protein. It is a hydrocarbon, i.e. a compound containing
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A strategy for ridding the world of VAD?

In July 2000, Time magazine announced that a potential solution to VAD had been found – ‘Golden Rice’ (Figure 8). This was a variety of rice that had been genetically modified to introduce β-carotene into the endosperm (part of the grain of the rice). The name arises from the fact that the otherwise white grains of rice are given a golden colour by the presence of carotenoid compounds.

The announcement came at the height of the global controversy over genetically modified
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Introduction to case study

In the previous section, you explored the science related to the development of the two traits found in the early commercial GM crops. Their production has been driven by commercial imperatives, and some of the widespread criticism of these crops has reflected a suspicion that they meet the needs of the multinationals’ shareholders, rather than those of wider society.

As biotechnological techniques have become more sophisticated, new types of crop have become possible, and in this sec
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3.2 Herbicide tolerance

As you discovered from Activity 1, herbicide tolerance is the trait most commonly incorporated into commercial GM plants. A crop can be made tolerant to herbicide by inserting a gene that causes plants to become unresponsive to the toxic chemical. Before considering how the genetic manipulation can be achieved, it is useful to understand a little about how herbicides act.

Many herbicides work by inhibiting a key plant enzyme necessary for growth (if you're not exactly sure what this mea
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3.1 Insect resistance

We will now look briefly at the science underlying the traits introduced into commercial crops, which you explored in Activity 1; a useful place to start is by considering how the property of resistance to insects is acquired by crops.

Insect damage causes huge losses of agricultural crops each year. For example, without co
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2.3 From infected cells to transgenic plants

Unlike the ‘natural’ infection process, where only the cells at the site of the crown gall are affected by the inserted T-DNA, scientists wanted to introduce new genes into all the cells of the plant. Fortunately, most plant cells are totipotent, which means that any cell from any part of the plant is capable of dividing into cells that can form any or all of the plant's tissues. This means that, using appropriate growth hormones and other tissue culture techniques, a single infect
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2.2 Using A. tumefaciens to genetically modify plant cells

Genetic engineers have capitalised on the fact that part of the DNA from the Ti plasmid of A. tumefaciens is integrated into the plant genome during the infection process. Ti plasmids can be isolated and a foreign gene spliced in at an appropriate point, making it possible to transfer the novel gene into the plant.

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Preamble

Your answers to Activity 1 will have revealed that the initial development of commercial GM crops has focused on the introduction of two traits: herbicide tolerance and insect resistance. However, many other traits have been introduced into crops that have yet to be grown commercially on any scale. These traits include characteristics such as resistance to viral, bacterial and fungal infections, stress tolerance (for example to high levels of salt in the soil), changes to flower pigmentation,
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Learning outcomes

By the end of this unit you should be able to:

  • understand more about the science that underlies the development of genetically modified organisms and in particular how gene transfer is brought about;

  • know something of the potential benefits and uncertainties associated with gene transfer and the high levels of technical ingenuity involved;

  • be better able to understand the science that underpins the development of Golden Rice and understand why the u
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Introduction

In recent years, scientists have made huge gains in their understanding of how genes can be altered and transferred from one organism to another – but that knowledge has been acquired amidst controversy and concern. The deep ethical concerns that have resulted from the emergence of genetic manipulation are explored in this unit. We begin with an examination of the basic structure and function of genes. A number of pioneering examples and techniques are explored, helping to explain why our p
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3 Summary

Hydropower was the earliest means of commercial electricity generation, and currently dominates alternative electricity supply. However, its global capacity for large-scale exploitation is less than six times that currently installed.

Growth of hydropower is slow and its contribution to global electricity supply is falling. Both are due to economic factors, the slow pace of large-scale project construction, the remoteness of high-potential sites, and increasing resistance to the social
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2 The future of hydropower

Hydroelectric power generators produce no emissions — except indirectly during their construction — and the water used is renewable. Generation can be started and stopped almost instantaneously, simply by opening or closing the inlets to the turbines. The generating technology is well-established. Other positive aspects of hydroelectric schemes are river regulation, and provision of irrigation and drinking water supplies, fisheries and recreational facilities.

These advantages have
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1 Hydropower

Hydroelectric energy is ultimately solar energy converted through evaporation of water, movement of air masses and precipitation to gravitational potential energy and then to the kinetic energy of water flowing down a slope. That energy was harnessed for centuries through the use of water wheels to drive mills, forges and textile works, before being supplanted by coal-fired steam energy. Electricity generation using water turbines, although first centred on constricted streams, has increasing
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Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions) and is used under licence.

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

Figures

Figure 3 Courtesy of Biophoto Associates;

Figu
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5 Summary of unit

We have seen in this unit that, despite having a high natural abundance, iron is in very short supply because of the insolubility of its oxides and hydroxides. A result of this is that organisms have developed methods for the uptake, transport and storage of iron. Bacteria, in particular, secrete very powerful iron chelators known as siderophores. Of all the iron–siderophore complexes, the iron(III)–enterobactin complex has the exceptionally high stability constant of 1049 mol<
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4.3 Iron storage

In humans, iron is stored mainly in the bone marrow, spleen and liver. About 10 per cent of all the iron in the body is in storage. Two proteins are involved in iron storage; these are called ferritin and haemosiderin (they also occur in other organisms). We shall only study the better characterised (and simpler!) ferritin.

Each ferritin molecule can store iron up to about 20 per cent of its total mass. This is a very high percentage, considering that less than 0.2 per cen
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4.2 Iron transport

It is obvious that iron must be transported around the human body. Firstly, it must be transported from the food in the gut to the places where it is required. Mostly, iron is required in the bone marrow, where red blood cells are formed. Red blood cells have a finite lifetime of about only four months, and old cells are destroyed, usually in the spleen. Iron from the destruction of these cells is then transported from the spleen back to the bone marrow to be recycled.

Iron cannot be tr
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3.1 How do organisms take up iron?

Nearly all organisms are able to take up iron. However, only a handful of organisms have had their iron-uptake chemistry studied. The organism that has received most attention (other than human) is a single-cell, prokaryotic bacterium (found in the human large intestine and elsewhere), called Escherichia coli (abbreviated to E.coli), a high-resolution image of which is shown in Author(s): The Open University

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