As individual human beings we are unique, shaped by our environment and experiences but also by the specific DNA sequences we have inherited. The extent and nature of variation in our DNA is remarkable with consequences ranging from physical appearance to risk of disease. With the rapid pace of advances in genetics over the last 20 years the amount of information related to human genetic diversity is at once overwhelming, and any review rapidly out of date. The intention of this book is not therefore to be exhaustive but rather to take a broader view using specific examples that illustrate the historical context of research in this area, and how it encompasses a range of scientific disciplines which have led to remarkable progress over a relatively short space of time. Just as the traveller with a round-the-world air ticket will not see the world in its entirety but will hopefully gain some appreciation of its extent and diversity, this book seeks to provide an overview of research into human genetic variation and some insight into its functional implications for health and disease.
This first chapter aims to provide a framework for understanding human genetic diversity by giving a detailed review of different types of genetic variation involving the genes encoding haemoglobin (Hb), the iron-containing protein found in red blood cells which is responsible for oxygen transport around the body. At first glance, this may seem too narrow a focus. However, by doing so we are entering regions of our genome remarkable for both the extent of their diversity, and the exhaustive research programmes over many years that have so elegantly delineated the nature and consequences of such variation. At the globin genes and neighbouring regions we can find examples of almost all known forms of human genetic diversity, many with dramatic consequences for human health. A discussion of the molecular basis of inherited disorders affecting haemoglobin (Box 1.1) will also allow an introduction to a number of fundamental concepts in human molecular genetics and a review of the often complex terminology used to describe genetic variation.
The pioneering work which has been carried out to understand genetic diversity at the globin genes (Fig. 1.1),
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