Antisense regulation of gene expression

The term antisense refers to the use of a nucleic acid that is complementary to the coding (i.e. ‘sense’) base sequence of a target gene. When nucleic acids that are antisense in nature are introduced into cells, they can hybridise to the complementary ‘sense’ mRNA through normal Watson-Crick base pairing. Synthetic antisense DNA chains as short as 15–17 nucleotides in length have been used to block specific gene expression by either physically blocking translation of the tar
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3.2 Higher-order DNA structures: DNA twisting and torsional effects

As discussed earlier, the helical nature of DNA results for the most part from the properties of the bases, their interactions and the geometry of the helix itself. There is, however, another important contributor to the structure of DNA that is found within the cell. The DNA helix is actually under a torsional stress due to what is called DNA twisting, which arises when the two strands of the helix are twisted around the axis, as shown in Figure 11a.


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1.2 Nucleic acids: genetic, functional and structural roles in the cell

The first role that one immediately thinks about for nucleic acids is that of an inherited genetic material, principally in the form of DNA. In some cases, the inherited genetic material is RNA instead of DNA. For example, almost 60% of all characterised viruses have RNA genomes and these are more common in plant viruses than in animal viruses. There is considerable variation in the amount of genetic material present within organisms (Author(s): The Open University

Learning outcomes

After studying this unit you should be able to:

  • define and use each of the terms printed in bold in the text;

  • understand the properties of nucleotides, how they contribute to secondary and tertiary structures of nucleic acids at the molecular level, and how torsional states are maintained in cellular DNA;

  • understand the different composition and roles of nucleic acids in the cell and their interactions with each other and with agents that cau
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Acknowledgements

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1.3 Summary of Section 1

  1. Water is a renewable resource; globally there is a virtually constant supply of fresh water, as water is recycled by natural processes, but it is unevenly distributed.

  2. A few litres of water per day are needed per person for human survival. For subsistence, the daily requirement is 20–40 litres per person; this includes the use of water for cooking and washing in addition to drinking, but not water for growing food. Water use in industrialise
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By the end of this unit you should be able to:

4.5 Generating carbon — the legacy of volcanoes

What is the origin of the carbon within the carbon cycle? Figure 1.9 showed that the great
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3.3 The Earth's internal heat

The occurrence of both volcanoes and hot springs shows that the Earth's interior is hot, producing molten rock at temperatures up to 1250 °C, and also superheated steam. However, these phenomena are mainly confined to several narrow zones along the world's active plate boundaries. Many measurements have now been made of the amount of heat flowing from the Earth's interior. Outside the distinctive zones mentioned above, heat flow varies from 40–120 milliwatts per square metre (mW m−2
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2.3 Broadband spectra

The broadband spectrum is the spectrum over all the observed wavelength ranges. To plot the broadband spectrum of any object it is necessary to choose logarithmic axes.

  • Why is it necessary to use logarithmic axes?

  • Because both the spectral flux density, Fλ, and the wavelength vary by many powers of 10.

Author(s): The Open University

3.3 The consensus conference concept

Consensus conferences were developed in the USA in the late 1970s. Originally called ‘consensus development conferences’, the National Institute of Health used these conferences as a means of fostering social acceptability of medical practices for which scientific expertise could not provide unequivocal answers to questions with a social dimension (Jørgensen, 1995). The success of consensus conferences in the USA meant that they were soon adopted in Europe. They have proved particularly
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7.5 Control measures

7.5.1 Control measures to avoid exposure

There are four main methods of exposure to chemicals:

  1. Inhalation – This is the main method of exposure to volatile solvents and gases.

  2. Skin absorption – Certain chemicals possess the ability to penetrate through pores of skin (for example, mercury compounds and hydr
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6.2 Chemicals (Hazard Information and Packaging for Supply) Regulations CHIP3

These regulations, which were first introduced in 1992, are known as CHIP1 and these were last revised in 2002 and called CHIP3. They are currently being revised again in 2005 to keep up with developments in the field of health and safety.

Figure 7

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Acknowledgements

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3.5 A new life

There is a common belief that life begins at the moment of conception, i.e. when a sperm fuses with an egg. This is a step forward from past years, when life was alleged to start at the time of ‘quickening’, i.e. when a woman could feel her fetus moving inside her. However, both these opinions suffer from an underlying falsehood: that life ‘begins’ at all. Life is a continuum; gametes are produced by living parents, and fuse to produce new living individuals, but unfused gametes are n
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Learning outcomes

After completing this unit you should be able to:

  • Define and use, or recognize definitions and applications of, each of the terms printed in bold in the text.

  • Explain the scientific basis for the main methods of contraception. (Question 1)

  • List the factors affecting fertilization. (Questions 2 and 5)

  • Describe with the help of diagrams the early stages of embryonic development. (Question 3)

  • <
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3.4.7 Induced earthquakes

Some reservoirs cause earthquakes to occur. This is perhaps not so surprising, as earthquakes are caused by stress in rocks, and the addition of a large mass of water in a reservoir on top of the rocks at the Earth's surface stresses the rocks and can trigger an earthquake. Not all reservoirs induce earthquakes: it is in general only the larger reservoirs, or the deeper ones (over 100m deep), and only if the reservoir is built in an earthquake area, releasing stress already stored in t
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Introduction

We have seen that where precipitation reaches the ground, some runs off the surface into streams and rivers and some of it infiltrates, passing through the soil. Water that reaches the water table to become groundwater may eventually re-emerge at the surface as springs where the water table intersects the surface. Almost all streams and rivers have springs or seepages as their ultimate source, or are fed by them at various points along their courses.

This unit is from our archive and is
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