Introduction

Living organisms use the components of the world around themselves and convert these into their own living material. An acorn grows into an oak tree using only water, oxygen, carbon dioxide, some inorganic materials from the soil, and light energy. Similarly a human baby grows into an adult by digesting and metabolising food and drink. The parents in each case pass to their progeny, or offspring, the information and specification for building cells from materials around them. This information lies in the genetic material, or DNA, which is found in the chromosomes within the nucleus and which is transmitted from generation to generation. Chromosomes can be regarded as strings of genes, the units of inheritance. It is to the study of chromosomes and genes that we now turn.

The idea of passing on information from parents to offspring raises an important question: how are the units of inheritance transmitted from one generation to the next? This course takes two approaches to answering this question. First, we look at what happens to the chromosomes of animals and plants during the process of sexual reproduction. Second, we examine how genes are transmitted in particular patterns from generation to generation. Then these two approaches are combined to show how the patterns of inheritance can be explained by the behaviour of chromosomes during sexual reproduction. Since genes are an integral part of chromosomes, following the behaviour of chromosomes allows us to trace the movement of genes. Thus the focus of this section will be at both the gene and chromosomal levels of explanation.

The majority of the study time will be dedicated to learning about genes and chromosomes and their patterns of inheritance. You will practise some basic maths skills, particularly the use of ratios and the mathematical idea of probability.