GENETICS

INTRODUCTION

The science of genetics sometimes seems rather remote from everyday life and from the business of providing direct care to patients and clients. In this unit, I aim to show you that this discipline can offer valuable insights to nurses, midwives and health visitors. These insights will assist in planning and delivering high-quality care.

As a scientific discipline, genetics requires an understanding of some elaborate and sophisticated concepts and a detailed knowledge of cellular structure and function.

These can only be achieved by lengthy study of the subject. They are the province of the professional geneticist. In this unit, I do not attempt to provide a watered down version of this professional training. No one would expect geneticists to deliver professional health care; similarly, health professionals are not expected to become biomedical scientists.

So rather than trying to cover the whole of the subject, I have selected four of the key concepts upon which this science is based. I have selected those concepts that are most relevant to the caring professions and which can be used to inform and improve practice. Each of the four sessions in this unit deals with one of these fundamental concepts, as follows:

This is intended to raise awareness of the differences between people, and how these can be explained. Such an understanding is essential in delivering individualised health care.

Many people are put off studying genetics by its numerical aspects. Session Two shows that an intelligent, professional interest in randomness is possible without any special mathematical knowledge.

This part considers how people adapt to particular environments and circumstances. This concept has been influential in the development of recent theories about nursing.

Understanding how and why things go wrong involves the idea of the vulnerability of the genetic material—an idea which relates to the day-to-day concerns of all members of the nursing profession.

In some ways, you could be at a disadvantage if you have studied genetics before starting this on unit. This is because I have adopted an approach which is different from the one found in standard textbooks. I have concentrated on those areas of the subject which can best inform practice in nursing, midwifery and health visiting and which will help practitioners to contribute to the current debates on the issues which arise from modern applications of this science to health care.

You may find that, even though non-technical language is used wherever possible, you need to spend quite a long time on some sections. The key genetic concepts may be challenging and unfamiliar. Please don’t worry if you find that progress is slow. It is worth persevering with these concepts, because they are so important to a clear understanding of many aspects of health care.

Below is a list of learning outcomes for each session in this unit. You can use it to identify your current familiarity with the subject, and so to consider how the unit can help you to develop your knowledge and understanding. The list is not intended to cover all the details discussed in every session, and so the learning profile should only be used for general guidance.

For each of the learning outcomes listed below, tick the box that corresponds most closely to your own abilities. This will provide you with an assessment of your current understanding and confidence in the areas that you will study in this unit.

CONTENTS

Introduction

Learning Profile

Session One

Variation    

Session Two

Randomness

Session Three

Adaptation  

Session Four

Vulnerability  

Learning Review  

Resource Section

1. Are homosexuals born and not made?

2. Gene therapy hope in muscular dystrophy

3. Wound healing under the microscope

4. Find out your future health

5. Nondisjunction of human autosomes:  sporadic Down syndrome

6. ‘Vaccine’ hope for malignant melanoma

7. Vehicle pollutants: effects on the lung

8. Radiant health?

9. Four short reports for use with Activity 48

10. Alzheimer’s disease: advances in genetics

Further Reading

Session One

I can:

explain the relevance of genetics to health-care practice
give a simple explanation of the way in which genetic and environmental factors give rise to observable differences between people
explain, in non-technical terms, the nature and origins of the genetic code
describe how the genetic code is organised into genes
give examples of the way in which the environment affects gene expression
apply these ideas to care planning.

I can:

explain the random nature of the inheritance of gender
explain how an understanding of the role of randomness in cell division enables genetic outcomes to be predicted
outline the basis of single-factor inheritance patterns
explain how random events contribute to genetic variation
describe the contribution of genes and the environment to the establishment of a ‘normal’ state
apply these ideas to care planning.

I can:

l explain the advantages for survival of ‘normal’ characteristics
l give examples of survival behaviour and explain its genetic basis
l outline the effects on health of moving between environments
l make links between the concepts of adaptation and health
l suggest why characteristics may persist despite being unfavourable
l apply these ideas to health-care practice.

I can:

summarise the causes of genetic variation
suggest how the environment can cause genetic damage
explain the links between random changes and ageing
outline how genetic repair mechanisms work
give examples of new developments in gene therapy
apply these principles to patient care.

 

SESSION ONE

Session One is divided into nine sections. Some are quite short, others are much more substantial. Each section ends at a natural break point, which will enable you to study in a series of fairly short sittings. On balance, the longer you study at one sitting, the less effectively you learn, so it is best to work for several short periods rather than one long one.

The aim of the session is to give you the opportunity to increase your awareness of the differences between people and to provide an explanation of this diversity.

This understanding will contribute to your ability to plan and deliver individualised care.

I will start by asking you to make some observations about the way in which people differ, particularly within families. These will be used as the springboard for an exploration of the causes of diversity and the nature of the genetic code.

The relationship between the theoretical elements and practical health care will be emphasised throughout. I will end Session One by applying the principles which have been developed to two contrasting, real-life case-studies.

• explain the relevance of genetics to health-care practice

• give a simple explanation of the way in which genetic and environmental forces give rise to the observable differences between people

• explain, in non-technical terms, the nature of the genetic code

• describe how the genetic code is organised into genes

• give examples of the way in which the environment affects gene expression

• apply these ideas to care planning.

Please note this text is written so that it can be understood by people who have not studied genetics at all in the past. It may be you have already achieved these outcomes and wish to use the material for revision purposes.

To begin with, we will think about some of the people we meet every day and see whether the science of genetics relates to some real-life questions. Here is a description of my own family.

All three members of my immediate family are ectomorphs – two very tall, slim sons and their tall, thin father. They have slim bodies, long limbs and they never gain weight. By contrast, both I and my parents are short and stocky.

One of our sons has very striking red hair. No other living member of either family has this feature, although my nephew has reddish blond hair. Apparently, my mother had two sisters with beautiful red hair. They both died of tuberculosis in their early twenties.

My mother’s surviving sister had two sons. The elder was classified as ‘mentally defective’, and died in an institution at the age of 16. His younger brother, born seven years later, was more fortunate. By then, more was known about the illness from which his brother had suffered. It was phenylketonuria (PKU) – an inherited disease for which all babies are now routinely tested at birth by means of a small blood sample taken from the heel. The younger boy had the same disease, but received treatment from birth.

When I think about my family and their characteristics, I can’t help asking certain questions. For example, suppose we had a daughter. Might she have been tall and slim with red hair? Is my red-headed son, like his great aunts, likely to be susceptible to TB? What are the chances that PKU will crop up again in future generations?

These are the kinds of questions which many people ask themselves from time to time. In asking them, we are starting to explore the science of genetics.

The description you have just read does not enable you to see the relationships between people in the family very clearly. A better way to do this is to draw a family tree. Geneticists have developed a particular way of doing this which is designed to make the connections as clear as possible by using a special set of conventions.

Figure 1 shows the family tree for red hair in my family, and includes an explanation of the conventions that are normally used in genetics.

A family tree - or pedigree for red hair

It would be too confusing to show more than one characteristics on a family tree, so it is usual to draw a separate diagram for each one.

Figure 2 shows the same family again, but this time it deals with PKU rather than hair colour.

Figure 2 A family tree for PKU

ACTIVITY ONE

ALLOW 20 MINUTES

Think about a family that you know well. It could be your own or someone else’s – that doesn’t matter, as long as you know something about at least three generations of the family. Can you identify a characteristic which has come and gone between the generations – like red hair in the family described earlier?

Write a short description of the family, and then draw a family tree to display it, using the symbols shown in Figures 1 and 2.

Commentary

How did you get on? Were you able to detect any characteristics that came and went between the generations?

The sorts of things that people identify when they try this exercise are usually striking physical characteristics – short legs, a prominent chin, an unusual hairline, baldness, protruding ears, strong teeth, and so on. This photograph of the Kennedy family shows several such striking physical characteristics:

Figure 3 Family characteristics in the Kennedy family

On the other hand, the characteristics you chose might have related to abilities – physical or mental – like being musical, athletic, or good at maths. Or, they could be illnesses or disabilities.

(End of Sample Material)