The human animal
Because the reader of this is presumably human, the author must go to great lengths to redefine to the reader what the reader is by nature. This process can be seen as symbolic and literal, because through analog, Ridley explains to the reader what the human being really is, literally speaking. Literally speaking, the human is an animal, with a lifespan just like any other animal, which was born and will die, and which is comprised from the DNA of its parents. This is obvious, but it is ironically contrary to the default perception most people have of their own self.
DNA as a mystery
The essays take the reader back in time to the era before the discovery of DNA, and then through drama, the essays describe the discovery of DNA by certain scientists. This use of narrative essay is designed to explain the essential mystery of DNA. We now understand what it is and how it works, but Ridley examines the past to find the time before such scientific discoveries. This raises the question about what we might learn in the future regarding life and biology.
The gene
To understand heredity, the reader must understand correctly what a gene literally is. This involves the establishment of a mental construct, because the gene is a unit of data too small to be perceived and too sophisticated to be inferred easily. A gene is a unit of data which can be passed down through a binary lottery system that occurs when sexual animals mate. This system can be called heredity, and through this system of chance, either a gene will remain for a new generation, or it will be lost, and some genes are dominant and others are not, so it is difficult to know which genes are being passed down.
The genome
This hypothetical construct is the complete understanding of human DNA and biology. By assembling a working definition for what each gene is and what it does, a person can learn about specific mutations and variations in specific human animals. This is important because it has meant (and will continue to mean) new medical breakthroughs; much of the book is dedicated to sharing the breakthroughs that have already been discovered by the scientific study of the human genome.
Life as a data transfer system
The book doesn't attempt to categorize life for its mystical, existential properties, because that would require philosophical speculation. Instead, Genome shows life descriptively, highlighting the mechanisms of life. Life can be seen mechanistically as a complex system of data transference, accomplished (at least as far as humans are concerned) through sexual procreation, through which various data bundles are combined. These data sets are DNA, and according to the data, a new animal body builds itself.
