3 The unique phenotype

3.1 Introduction

We each begin life with a unique genome. As we grow and develop, we are each subjected to a range of factors that influence the way development proceeds. Most of those factors are common to us all, the intracellular and intercellular signals, hormones, birth, milk. But the precise combination and the range and duration of those factors varies between individuals, such as the duration of gestation or the composition and quantity of a mother's milk, for example. In addition we each undergo different experiences, injuries and illnesses. What and who we are is our phenotype and it depends on all these factors. And because no two people have all these factors in common, each person (each phenotype) is unique.

Let us now consider in a little more detail some of those factors and how they influence our phenotype.