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Learning outcomes

After studying this unit you should know:

  • the number of chromosomes is characteristic of each species and can vary enormously between species

  • genetics is based on the concept of the gene as the unit of inheritance

  • that sexual reproduction always includes two distinctive processes: the production of gametes, which involves meiosis, and fertilisation. The two processes are accompanied by changes in the chromosome number, from diploid to haploid and fr
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Introduction

This unit looks at how units if inheritance are transmitted from one generation to the next. First you will look at what happens to the chromosomes of animals and plants during the process of sexual reproduction. Then you will examine how genes are transmitted in particular patterns from generation to generation. These two approaches combine to illustrate how the patterns of inheritance can be explained by the behaviour of chromosomes during sexual reproduction.

This unit is from our ar
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Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions). This content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence

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

The content acknowledged be
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6.3 Risk

Risk is a difficult concept. Most of what we do in life involves making choices and taking risks. Sometimes the risks are small, and sometimes they are large. It can be difficult sometimes to know what the risk of doing something is. Past experience can also influence the way we think about risk. If one was knocked over by a car crossing the road, then even though the risk of it happening again is small we may remain worried and concerned about crossing the road.

How you explain risk is
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11 The official inquiries

In December 1997, the UK government announced the Public Inquiry into BSE that was to be chaired by Lord Justice Phillips. Public hearings commenced in March 1998 and eventually concluded in December 1999. The Report of the BSE Inquiry was delivered to the Secretaries of State for Agriculture, Fisheries and Food and for Health and published in October 2000. Having published an interim response in February 2001, the government's final response to the report was published in September 2001. As
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10 Managing the BSE/vCJD episode from March 1996

In March 1996, SEAC announced that the CJD Surveillance Unit had identified vCJD as a new human disease, the first death from which occurred in May 1995. SEAC concluded that, although there was no direct evidence of a link, the most likely explanation for vCJD was exposure to BSE before the SBO ban was introduced in 1989. At the time, the strongest evidence for the link was that vCJD was a new TSE in humans (the symptoms of which differed from previously known human TSEs) that had aris
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1 Overview

As you work through this unit you will come across boxes, like the one below, which give you advice about the study skills that you will be developing as you progress through the unit. To avoid breaking up the flow of the text, they will usually appear at the start or end of the sections.

As well as the unit text, you will be using The Life of Mammals book (LoM) and related The Life of Mammals DVDs, as described in the introduction to this unit. Before you go any further,
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1.5.3 A note on functions and derivatives

This subsection introduces two crucially important mathematical ideas, functions and derivatives, both of which are used throughout physics.


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6.2 Producing the radioactive substance (elution)

In the radiopharmacy Tc-99m is produced in a generator.

Mo-99, a product of the fission of uranium, is isolated from a nuclear reactor and absorbed on to an alumina column in the generator. When a saline solution is passed over the column, ion exchange results in the production of sodium pertechnetate. This can then be chemically manipulated to form a variety of compounds. The removal of the technetium by the passage of saline is known as elution.

Conveniently, the optimum interva
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2.2.2 Collimator

The dimensions of the emerging X-ray beam can be altered by the collimator. This helps to ensure that only the region of interest is exposed to the X-rays.


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Introduction

This course is about the scientific basis of medical imaging. Imaging techniques have long been part of the physician's diagnostic repertoire. Their use has been developed from simple X-ray measurements in the Accident and Emergency Unit to a range of subtle investigations of both the structure and functional status of targeted organs, including the brain. Medical imaging is at the heart of contemporary medical practice.

This unit is an adapted extract from the Open University course
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2.3.2 The crater Pwyll

You might also have noted that there are no obvious impact craters visible in Figure 16 (see Section 2.3.1). In fact there are a few. One is a bright spot, 15 km in diameter, surrounded by a dark halo of ejecta that occurs 10 mm from the top edge and 65 mm from the left-hand edge of the figure. Another is a s
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4 Germline gene therapy

Now that in vitro fertilization – bringing eggs and sperm together outside the prospective mother's body – is an established technology, the possibility exists that genes could be altered in eggs or sperm, or in a very early embryo. The obvious advantages of germline gene therapy are that the cells are accessible (because they are outside the body), so gene delivery is less of a problem than it tends to be with somatic cells; and the inserted gene (or genes) would be present
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2.2 Energy flow in ecosystems

You are about to meet some very large numbers, expressed in scientific notation, and some new units. The new units are those that are used to measure the amount of solar energy received by a part of the Earth's surface. Since plants are dependent on light for photosynthesis, the amount of plant material that ca
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3.1 Speed and endurance

The first question in this section is a mathematical one, in which you are asked to convert from one set of units to another. If you have been following the advice in previous units in this series, you will be reading km h−1 as kilometres per hour and you will probably already think of m.p.h. as mi
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8.3 Shortage of minerals

You may be familiar with salt licks that are provided for domesticated cattle. In the wild, grass is also often low in minerals (e.g. it has almost no sodium and very little calcium), so grazers may have to go to extraordinary lengths to supplement their diet with additional minerals obtained from the most unlikely places. LoM gives some examples, but the most impressive activity takes place in the caves of Mount Elgon in Kenya [pp. 113–114]. You'll probably recall this spectacular footage
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5.2 Pseudo-ruminants

Animals in the third suborder of the Artiodactlya, the pigs, peccaries and (according to most authorities) the hippopotamuses (suborder Suina), use a slight variant on the ruminant method, and are often referred to as pseudo-ruminants. You might like to add this information to your version of Table 2. These animals do have st
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4.2 Digesting cellulose

Figure 3 in this section contains a lot of information and many terms that are probably new to you. Set aside the detail for the moment, read
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3.6 The numbers game … or the struggle for existence

In the majority of The Life of Mammals TV sequences there is relatively little evidence of any struggle for existence, apart from the occasional predator/prey interaction. Even then you are offered the comforting reassurance that ‘four out of five chases end with the prey escaping’. So you could be forgiven for thinking that most mammals survive to a ripe old age, or at least until, like the topi, they have fulfilled their reproductive potential. Not so! Four out of five chases may
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Introduction

Sixty-five million years ago, animal and plant life were very different from nowadays, but there were rat-sized placental mammals living successfully on the ground. They were insect eaters, i.e. insectivores, feeding on the vast numbers of insects and other invertebrates living in soil, leaf litter and low-lying vegetation. Insectivore means ‘insect eater’, and in this unit we will explore the world of insect-eating mammals, classified together on the basis of a reasonably close evolution
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