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2.3 Scaling up

They may look at dozens of alleles, and involve thousands of people, but existing screening programmes have been concerned with individual genes. But the technologies now being developed will soon permit the recording of hundreds of genes at a time. So-called gene chips combine the skills of microchip designers with DNA sequence information to offer rapid, easy-to-read results for an individual covering hundreds of genetic variants. A gene chip is a thin slice of glass about the
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2.2.4 Longer-term considerations

Something else to ponder is the effect that screening might have on the longer-term incidence of disease and (not the same thing) on the incidence of gene variants linked to disease. Sometimes, the impact on a disease can be dramatic. Take thalassaemia, a haemoglobin disorder similar to sickle cell disease, in which premature destruction of haemoglobin-containing red blood cells leads to anaemia. It is relatively common in some Mediterranean countries. Like sickle cell disease, it is understo
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2.2.3 Cystic fibrosis

A different model for the genetic tests of the future is screening for cystic fibrosis (CF). This is a DNA-based test, which became possible after the gene involved in CF was identified in 1989. CF is a recessive disease, and it should be easy to test to see if prospective parents carry a mutated allele. A simple mouthwash yields enough cells for DNA extraction. If both partners are carriers, they can consider further counselling before conception, and/or pre-natal testing of any potentially
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2.2.1 Phenylketonuria

The classic example of population screening is testing new-born babies for phenylketonuria (PKU). Individuals with PKU fail to make a protein, a certain enzyme, and develop mental retardation. The absence of the enzyme results in both an accumulation of phenylalanine, which causes the mental retardation, and a deficiency of tyrosine in the body, as shown in Author(s): The Open University

2.2 Population screening for genetic disease: the precedents

Knowing about particular genes, or their effects, also permits screening – the search in a population for persons with certain genotypes that are associated with a particular disease. Thus the test may be offered to one and all. Until now, screening programmes have focused on one gene at a time, or one disease at a time, in cases where a mutated gene poses serious health problems and something can be done for those who are found to carry the mutation. What that something is varies with the
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Learning outcomes

After studying this unit you should understand:

  • some of the ways in which genetic knowledge could affect medical practice, in particular in relation to predictive medicine

  • how populations are screened for conditions such as phenylketonuria and whether screening could be used for carriers of recessive genetic disorders such as cystic fibrosis

  • how gene chips may be used to screen for large numbers of genes at once, making it possible to predict the li
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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 1 Science Photo Library;

Figure 8a This photograph has been provided by Railway Technical Research Institute in Japan;

Figure 22 Proceedings of the Royal Society A248 464. The Royal Society;

F
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1.8.3 Explaining the observations

Having made and reviewed our observations, we are now in a position to interpret them – why are the rocks the way they are? The sedimentary strata that we see in Figure 16 were likely to have been deposited in essentially horizontal layers, so why is one set tilted and the other horizontal? To answer
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Learning outcomes

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

  • explain the difference between a mineral and a rock;

  • describe the textural differences between igneous, sedimentary and metamorphic rocks;

  • account for these differences in terms of the processes that produce these rocks;

  • classify igneous rocks according to their grain size and mineralogical composition;

  • recognise the difference between a body fossil and a trace fossil;

    <
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5.2 Neural ageing: article 2

In the article presented here by Esteban (2004) entitled ‘Living with the enemy: a physiological role for theβ-amyloid peptide’, Trends in Neurosciences, 27, pp. 1–3, the author introduces us to a very important molecule implicated in the aetiology of Alzheimer's disease. However, the β-am
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5.2.2 Calorie restriction

Since the publication of Osborne, Mendel and Ferry's paper (Science, 1917, Vol 45, pp. 294–5) calorie restriction has been the most reliable method of extending the lifespan of laboratory animals. These results have been confirmed by many researchers and have been extended to a variety of verteb
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2.1.3 Reflective diffraction gratings

Although the above description of diffraction has been in terms of light passing through a series of slits in a (transmission) diffraction grating, the type of grating which is currently most common in astronomy is a reflective diffraction grating or reflection grating. This again exploits the wave properties of light, in this case by making adjacent sections of a wavefront travel extra distances as it is reflected off a non-uniform surface. The non-uniform surface is actually a
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1.7 Summary of Section 1 and questions

  • Converging lenses or mirrors cause parallel beams of light to be brought to a focus at the focal point, situated at a distance of one focal length beyond the lens or one focal length in front of the mirror. Diverging lenses or mirrors cause parallel beams of light to diverge as if emanating from the focal point of the lens or mirror. Light paths are reversible, so a converging lens or mirror may also act as a collimator and
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1.1 A milestone in the advancement of astronomy

Unaided human eyes, well as they may serve the needs of everyday life, are not very suitable for detailed astronomical observation. First, the eye has a limited sensitivity. A distant source of light, such as a star, will not be seen at all unless the intensity of light from it reaching your eye is above the sensitivity threshold of the retina. Second, the ability of the eye to distinguish fine detail is limited by the finite physical size of the detectors on the retina and by the small apert
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References

Baker, J. M. R. (1992) Body condition and tail height in great crested newts, Triturus cristatus, Animal Behaviour, 43, pp. 157–159.
Bronson, F. H. (1987) Environmental regulation of reproduction in rodents. In: Psychobiology of Reproductive Behavior, D. Crews (ed.), Prentice Hall, New Jersey. p. 209.
Hedenstrom, A. and Alerstam, T. (1992) Climbing perfo
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1.5.6 Copyright - what you need to know

An original piece of work, whether it is text, music, pictures, sound recordings, web pages, etc., is protected by copyright law and may often have an accompanying symbol (©) and/or legal statement.. In the UK it is the Copyright, Designs and Patents Act 1988 which regulates this.

In most circumstances, works protected by copyright can be used in whole or in part only with the permission of the owner. In some cases this permission results in a fee.

However, the UK legislation inc
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7.4.3 Modelling errors

  • be aware that it is often possible to provide an estimate of error for numerical values derived from the application of theoretical models to a data set.

For me, thinking about the use of models convinces me of some of the benefits of ‘problematising’ science – as we've been doing in the commentary so far. Indeed, my feeling is that using models reflects something more general about how scientific understanding is built up. By this I me
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7.3 Multiple interpretations in science

Talking of media reports of the Chernobyl episode, Millar and Wynne point out that:

[disagreements between scientists] become difficult to interpret, other than in terms of bias or incompetence. Divergences between the data and interpretations of pressure groups … and the official sources are attributed to the former [bias]; those between different official agencies … to the latter [incompetence]. Only in a han
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Introduction

This unit is designed as an introduction to the academic study of the concept of rules, but will also serve as an introduction to a variety of different writing styles that are used in the academic world. It will challenge you to think about why some statements are rules and some are not, and what it is that distinguishes rules from habits and customs. It also looks at more formal rules and how such rules are applied and enforced. Rules shape our lives because they set out what we may and may
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