In his book entitled “Genome”, Matt Ridley takes us on a ride through the human genome, recently sequenced, one chromosome after another from the largest to the smallest, from 1 to 23, including the X or Y that distinguishes men and women. For each chromosome, he picks a different gene or feature and tells a story about it. Some of the stories are outlined below.

The chapter called “Life” describes the probable origin of life, from the “RNA world” on. No particular human gene is evoked here. The next chapter entitled “Species” compares chimps and humans, so close and yet so different. The third chapter-called “History” describes the discovery of DNA structure by Watson and Crick, a feat that happened not so long ago; yet since then, we have cracked the genetic code and mastered ways of bio-engineering genes.

Chapter 4, “Fate”, is the first to pick out a gene for comment. It is the gene for Huntington’s disease. (That is the wrong phrase: the normal gene causes no disease, only the mutated gene does. But the short-hand phrase is so often used in describing genetic diseases.) The ethical question is: since it is now possible to predict if you will have the disease later in life, do you want to know? About half the people at risk take the test, in order to know whether to avoid having children; the other half choose not to be tested; they want to stay happy themselves without that precaution.

Chapter 5 (and gene 5) refers to asthma, a disease partly genetic and partly environmental – so which gets the blame? In any case, its frequency is increasing, so maybe we should decrease pollution.

Chapter 6 (“Intelligence”) discusses the vexing question of IQ testing, and what it really measures. IQ measures are about 70% genetic, but no single “IQ gene” has been isolated.

Chapter 7 (“Instinct”) concentrates on human language, which, according to Noam Chomsky, is hardwired in the human brain (animals lack language), but not controlled by a single gene.

Chapter 8 (“Conflict”) discusses the antagonism between imprinted (maternal or paternal) genes (a new discovery) and the interplay between X and Y chromosomes. Battle of the sexes on the nano scale.

Chapter 9 is largely about human blood groups and the intricate relationships between them. The various blood proteins involved are strictly under genetic control.

Chapter 10 (“stress”) is about cortisol and other hormones, and the difference between sudden fear (which is useful) and prolonged anxiety (which is harmful.

Chapter 11 (“Personality”) discusses different psycho logical types and the neurotransmitters that mediate them.

Chapter 12 (“Self-assembly”) tells about fetal development, and how genes are turned on and off in a sequence strictly regulated by homeo-box genes.

Chapter 13 (“Pre-history”) deals with correlations between language families, racial groups, and the history of the geographic spread of human groups from Africa to all regions of the world.

Chapter 14 (“Immortality”) is about aging and cancer, and the influence of telomerase and oxygen free radicals.

Chapter 15 (“Sex”) deals with sexual abnormalities at birth, due sometimes to the failure of the testosterone signal in early fetal development, and with trans-sexual transformation.

Chapter 16 (“Memory”) tells about the Baldwin effect, which causes the transfer of parental experience to the child in a quasi-Lamarkian way – but really strictly genetic and Darwinian.

Chapter 17 (“Death”) discusses the role of cell apoptosis in cancer cells and in some normal development proesses, such as early embryonic neuron connections and immune cell “education” not to “recognize” self.

Chapter 18 (“Cures”) is about future possibilities of genetic medicine, particularly in the case of SCrD (an inherited immune deficit.)

Chapter 19 (“Prevention”) talks about possibilities of preventing Alzheimer’s disease, which is partly genetic, especially in the early-onset variety.

Chapter 20 is “about Mad Cow Disease and its human version, Creutz-Jacob disease. Surprisingly, it is caused by a mutation in prions, purely protein particles without any DNA or RNA, smaller than a virus. prions act by changing their configuration and cause other normal prions changing configuration too. Who says that proteins cannot act as reproduction templates?

That is the end of chromosome-inspired chapters; but two more chapters follow: Chapter 21 (“Politics”) discusses eugenics, pro and con. Chapter 22 attacks the problems of free will versus determinism.

On the whole, Ridley leans toward “Nature” rather than “Nurture”, while stressing interactions, and even finding a niche for free will.

Later addition: The place of some genes on chromosomes. This is only a very small sampling, since there are some 100,000 genes, or at least 38,000 according to a later estimate.

Chromosome

1
2 – HOX // ____CREB (memory)
3
4 – Huntington’s disease // ____alcohol tolerance
5 – Asthma
6 – Dyslexia // ____IQ
7 – Cyctic fibrosis // ____HOX // ____language
8 – Maternallpaternal imprinting
9 – Blood groups // ____HOX
10 – stress (anxiety), cortisol
11 – Risk-taking // ____personality types // ____sicklecell anemia
12 – HOX // ____fetal development
13 – Breast cancer
14 – Aging // ____cancer
15 – Eye colour // ____hair colour // ____Tay-Sachs disease // sex abnormality at birth
16 – Thalassemia // ____CREB (memory)
17 – Breast cancer // ____apoptosis // ____athletic talent// HOX
18 – SCID
19 – Alzheimer’s disease
20 – Creutzfeldt-Jakob disease
21
22
XY – Homosexuality, colour blindness