"How does the body push the comparatively tiny genome so far? Many researchers want to put the weight on learning and experience, apparently believing that the contribution of the genes is relatively unimportant. But though the ability to learn is clearly one of the genome's most important products, such views overemphasize learning and significantly underestimate the extent to which the genome can in fact guide the construction of enormous complexity. If the tools of biological self-assembly are powerful enough to build the intricacies of the circulatory system or the eye without requiring lessons from the outside world, they are also powerful enough to build the initial complexity of the nervous system without relying on external lessons.

The discrepancy melts away as we appreciate the true power of the genome. We could start by considering the fact that the currently accepted figure of 30,000 could well prove to be too low. Thirty thousand (or thereabouts) is, at press time, the best estimate for how many protein-coding genes are in the human genome. But not all genes code for proteins; some, not counted in the 30,000 estimate, code for small pieces of RNA that are not converted into proteins (called microRNA), of "pseudogenes," stretches of DNA, apparently relics of evolution, that do not properly encode proteins. Neither entity is fully understood, but recent reports (from 2002 and 2003) suggest that both may play some role in the all-important process of regulating the IFS that control whether or not genes are expressed. Since the "gene-finding" programs that search the human genome sequence for genes are not attuned to such things-we don't yet know how to identify them reliably-it is quite possible that the genome contains more buried treasure."

What propels an embryo from one stage to the next-and makes one species different from another-is not a blueprint but rather an enormous autonomous library of the instructions contained within its genome. Each gene does double duty, specifying both a recipe for a protein and a set of regulatory conditions for when and where it should be built. Taken together suites of these IF-THEN genes give cells the power to act as parts of complicated improvisational orchestras. Like real musicians, what they play depends on both their own artistic impulses and what the other members of the orchestra are playing. As we will see in the next chapter, every bit of this process-from the Cellular Big 4 to the combination of regulatory cues-holds as much for development of the brain as it does for the body.

The biological goal of the existence of every organism becomes understandable when we realize that it acts as a protector of genes worn in it, which must ensure that they move into the child's body before the caregiver himself becomes old and can not function properly.

Recent genome-sequencing efforts have confirmed that traditional "good-citizen" genes (those that encode functional RNA and protein molecules of obvious benefit to the organism) constitute only a small fraction of the genomic populace in humans and other multicellular creatures. The rest of the DNA sequence includes an astonishing collection of noncoding regions, regulatory modules, deadbeat pseudogenes, legions of repetitive elements, and hosts of oft-shifty, self-interested nomads, renegades, and immigrants. To help visualize functional operations in such intracellular genomic societies and to better encapsulate the evolutionary origins of complex genomes, new and evocative metaphors may be both entertaining and research-stimulating.

Yori, Human purpose isn't what you say it is or what I say it is. It's what your biology says it is—what your genes say it is.

[G]enes make enzymes, and enzymes control the rates of chemical processes. Genes do not make “novelty seeking” or any other complex and overt behavior. Predisposition via a long chain of complex chemical reactions, mediated through a more complex series of life's circumstances, does not equal identification or even causation.

Genes are recipes for both anatomy and behaviour.

Every time a is needed, the appropriate chemical 'code' is 'read off' the ; this gives the pattern of chemical elements that will make that what it is. Our genes encode the sequences of 100 000 or so proteins that make up the human body.

Instead, in our world, nature's contribution to development comes not by providing a finely detailed sketch of a finished product, but by providing a complex system of self-regulating recipes. Those recipes provide for many different things-from the construction of enzymes and structural proteins to the construction of motors, transporters, receptors, and regulatory proteins-and thus there is no single, easily characterizable genetic contribution to the mind. In the ongoing, everyday functioning of the brain, genes supervise the construction of neurotransmitters, the metabolism of glucose, and the maintenance of synapses. In early development, they help to lay down a rough draft, guiding the specialization and migration of cells as well as the initial pattern of wiring. In synaptic strengthening, genes are a vital participant in a mechanism by which experience can alter the wiring of the brain (thereby influencing the way that an organism interprets and responds to the environment). There are at least as many different genetic contributions to the mind and brain as there are genes; each contributes by regulating a different process.

Genes are biochemical recipes written in a four-letter alphabet called DNA.

In the years to come, some of our best minds will try to dig deeper into that computer program, to figure out its individual lines of code (the IF-THENS that we call genes), the products of those lines (what we call proteins), how all those lines of biological code fit together, and how they make room for nurture.

In the long run, the effects on society will be profound. Take, for example, the advances that our increasing understanding of genes will lead to in medicine. Because, as we have seen, the brain is built like the rest of the body, it is also amenable to many of the same types of treatment. For example, stem cell therapies originally developed for leukemia are being adapted to treat Parkinson's disease and Huntington's disease. Gene therapies developed for cystic fibrosis may someday help treat brain tumors. Both work by harnessing the body's own toolkit for development.

Genes do indeed behave as if they have selfish goals, not consciously, but retrospectively: genes that behave in this way thrive and genes that don’t don’t.

The genes are the master programmers, and they are programming for their lives.

Complex organisms cannot be construed as the sum of their genes, nor do genes alone build particular items of anatomy or behavior by themselves. Most genes influence several aspects of anatomy and behavior—as they operate through complex interactions with other genes and their products, and with environmental factors both within and outside the developing organism. We fall into a deep error, not just a harmful oversimplification, when we speak of genes “for” particular items of anatomy or behavior.