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4.4 Incorporating substantial equivalence into national and international law

The concept of substantial equivalence very quickly became important in international trade law. The WTO aims to harmonise national food standards to meet international norms. Under its rules, a country could be penalised if it imposed food standards more stringent than those agreed internationally. In this context, international food standards are set by the Codex Alimentarius Commission (Table 1). In 1996, a report was issued within the Codex framework, which endorsed the principle of subst
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3.2 Communicating Pusztai's findings

In mid-1998, the Rowett Institute released a succession of press releases describing Pusztai's findings. The safety, or otherwise, of GM foods was a hot issue at the time and his preliminary findings gained widespread publicity. Pusztai gave an extended interview to the World in Action TV programme ‘Eat up your genes’, broadcast in August 1998. He described some of his experiments and outlined his interpretations in ways that helped shape the general tone of the programme, which was highl
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3.1 Pusztai's experiments

Issues of ‘fairness’ and our obligations to the developing world do not in themselves explain why the issue of GM plants attracts such controversy. This section focuses on an episode in the fraught history of the development of GM foods that had a significant effect on public attitudes in the UK. In particular, we look at the experiments of Arpad Pusztai in the late 1990s at the Rowett Institute near Aberdeen, Scotland. These experiments are of particular interest to us because they revea
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2.4.1 The second generation of GM crops

Much of the present-day debate about GM plants centres around the existing range of GM crops, most of which have been engineered for herbicide tolerance or insect resistance (covered in unit S250_1 Gene manipulation in plants). One of the implications of this narrow commercial focus is that the benefit that such crops would bring, other than to those multinational companies that produce them, is by no means clear. Weighing up their value on some form of ethical scales might be unlikely
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2.2.1 Do GM crops pose unique problems?

It is perhaps overly simplistic to take the line that only ‘natural foods’ should be commended and that GM plants are unnatural. Arguably, very few of our modern foodstuffs can be termed ‘natural’, in that they are not derived from naturally evolved crops. Tremendous changes in genetic make-up have been achieved by conventional (i.e. non-GM) breeding methods. Traditional plant breeding involves selection of individuals seen as superior, and then crossing, i.e. transferring the pollen
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1 Preamble

S250_1, Gene manipulation in plants focused predominantly on the science behind a number of transgenic crops, but also explored some of the social issues surrounding the development of Golden Rice. This unit will focus less on the science as such, but will explore some of the emerging social concerns.

Many of the issues that surround GM crops are ethical. They relate to what course of action is ‘right’, and initially Section 1 of this unit will explore a number of arguments from the
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3.1.3 Observing through the interstellar medium

  • Material in the interstellar medium absorbs radiation. An extra term, A, the absorption in magnitudes, is required in Equation C:

  • Radiation is both scattered and absorbed by interstell
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3.1.2 Star clusters and stellar evolution

  • Since all the stars in a cluster formed at about the same time, and all have similar compositions, they provide a powerful tool for the study of stellar evolution.

  • The lack of massive stars lying at the top of the main sequence in clusters indicates that they evolve fastest. The ages of clusters are inferred from the position of the main sequence turn-off.


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3.1 The H–R diagram

  • The Hertzsprung-Russell (H–R) diagram displays the photospheric temperatures and luminosities of the stars. The corresponding radii are obtained from Equation A. The H–R diagram is a very useful aid to our understanding of the stars and their evolution.

  • The stars tend to concentrate into certain regions of the H–R diagram, and so some combinations of temperature and luminosity occur far more commonly than others. These concentrations
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2.5 Using stars to probe the interstellar medium

The effects of interstellar material on starlight can be used to probe the properties of the interstellar medium itself. A few examples are:

  • The presence of particular interstellar atoms or molecules may be determined by identifying the observed spectral lines or bands.

  • The temperature of the gas may be determined from the relative strengths of different lines or bands produced by different energy state changes of the same atom or mol
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1.3 How can we explain the distribution of stars on the H–R diagram?

Here is a possible explanation for the concentration of stars into certain regions on the H–R diagram. It is based on the reasonable assumptions that:

  • Any particular star is luminous for only a finite time;

  • There are distinct stages between the star's cradle and grave, each stage being characterized by some range of temperature and luminosity; the star thus moves around the H–R diagram as it evolves;

  • The stars we
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1.2 The main classes of stars

The main classes of stars are shown in Figure 5.

The main sequence is ‘main’ in the sense that about 90% of stars fall into this class, and ‘sequence’ in the sense that it is a long, thin region that trails across the H–R diagram, covering a very wide range of temperatures and luminosities. The Sun i
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2.1 Degrees of torpor

Adaptive hypothermia occurs in at least six distantly related mammalian orders (Table 1) and in several orders of birds. There is a spectrum running from those species which can tolerate a drop in T b by 2° C for a few hours, to the seasonal deep hibernators which maintain a T b as low as 4° C for weeks on end.

Table 1 Groups o
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5.3 Metabolism

Molecules diffuse more slowly at low temperature: measurements of the rates of diffusion of small molecules such as lactic acid, Ca2+ and analogues of glucose and ATP through fish muscles produced Q10 values of 1.75–2.04 between 5 and 25° C. Nearly all enzyme reactions are slower at low temperatures (although sometimes whole pathways can be faster if an inhibitor is more inhibited by low temperature than are the catalysts). So, in the absence of temperature compensat
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8.2 Wilson's disease

The effects of a protein that is absent, or present but not doing its job, may not be evident for many years. This is called late onset, and is exemplified by Wilson's disease. Many molecules within the body require small amounts of minerals such as iron, magnesium or copper to function properly. There are mechanisms for absorbing these minerals from the diet. However, in excess, these same minerals can be toxic, as is the case with copper. So there are also mechanisms for getting rid
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7.8 Summary of Section 7

This section has sought to illustrate the formation of connections between neurons and their targets by exploring a few examples. The picture that emerges is one of cells at different stages of development subjected to a vast array of signals. These signals are the medium through which environmental factors exert their effects. To some of these signals, some cells respond; to other signals, other cells respond. What a cell, a neuroblast, a growth cone actually does is dependent on the combina
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3.6.5 Folate (folic acid, vitamin B9)

Folate is a generic name for a group of related compounds. The name ‘folate’ was based on the word ‘foliage’, after it was identified in a crude extract from spinach, though it is also found in liver, other green vegetables, oranges and potatoes and it is often added to breakfast cereals (usually listed as folic acid). Folate is less sensitive to heat than many of the B vitamins, though it is destroyed if food is reheated or kept hot for long periods. Folate is involved in amino acid
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1.1.1 The chemical structure of DNA

This unit explores the chemical nature of the genome. Genomes are composed of DNA, and a knowledge of the structure of DNA is essential to understand how it can function as hereditary material. DNA is remarkable, breathtakingly simple in its structure yet capable of directing all the living processes in a cell, the production of new cells and the development of a fertilized egg to an individual adult.

DNA illustrates beautifully the precise relationship between molecular structure and b
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3.1 A two-fluid model

As was mentioned earlier, a substantial dose of quantum mechanics would be required to provide a full explanation of the properties of superconductors. This would take us too far away from electromagnetism, and we shall therefore restrict our discussion to aspects that can be discussed using classical concepts of electromagnetism.

We shall model the free electrons within a superconductor as two fluids. According to this two-fluid model, one fluid consists of ‘normal’ electron
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1 Superconductivity

Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes (Figure 1) as he studied the properties of metals at low temperatures. A few years earlier he had become the first person to liquefy helium, which has a boiling point of 4.2 K at atmospheric pressure, and this had opened up a new range of temperature to experimental investigation. On measuring the resistance of a small tube filled with mercury, he was astonished to observe that its resistance fell from ~0.1 Ω at a temper
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