Introduction

You have probably noticed that parents share many or most of their traits with their offspring. This observation came to the attention of humans long before scientific investigation developed. Human curiosity about the basis of trait inheritance is long standing, but most of what we know about genetics has emerged through research from the past 100 years. The fundamental concepts of trait inheritance in sexually reproducing species will be described in this lesson. The classical experimental approach that revealed these principles will be described in the following two lessons. For now, we will focus just on the facts of how variation is inherited.