Genome (book)

Genome: The Autobiography of a Species in 23 Chapters is a 1999 popular science book by Matt Ridley, published by Fourth Estate.

Chapters

The book devotes one chapter to each pair of human chromosomes. Since one (unnumbered) chapter is required to discuss the sex chromosomes, the final chapter is number 22. Ridley was inspired to adopt this model by Primo Levi's book The Periodic Table.

Chapter One, Life

The first chapter begins with a quote from Alexander Pope on the cycle of life. The very broad topic "Life" is also the topic of the chapter. Ridley discusses the history of the gene briefly, including our "last universal common ancestor" or "LUCA".

Chapter Two, Species

Ridley discusses the history of human kind as a genetically distinct species. He compares the human genome to chimpanzees, and ancestral primates. He also points out that until the 19th Century, most scholars believed that there were 24 sets of genes, not 23 as known today.

Chapter Three, History

This chapter discusses the interplay between early geneticists, including Gregor Mendel, Charles Darwin, Hermann Joseph Muller and Francis Crick among others.

Chapter Four, Fate

Huntington's Corea is used to discuss the use of a particular sequence on Chromosome Four to cause traumatic health consequences. The search for the chromosomal source of this and other related diseases is discussed through the work of Nancy Wexler, someone who may have inherited the gene but who turns to scientific work to study it in others.

Chapter Five, Environment

The concepts of pleitropy and genetic pluralism are introduced. A brief history of the study of asthma is used as the case study. Asthma is related to as many as fifteen different genes, many on chromosome five. Specifically, this includes a change from adenosine (A) to guanine (G) at position 46 on the ADRB2 gene. The ADRB2 gene is related to the control of bronchodialation and bronchoconstriction.

Chapter Six, Intelligence

Robert Plomin's announcement in 1997 of the discovery of a gene for "intelligence" on chromosome 6 is the foundation for this chapter's lengthier discussion of the genetic basis for intelligence. This included gene IGF₂R on the long arm of chromosome 6. This gene may also be related to liver cancer. Ridley continues his premise in this chapter that the use of simple genetic markers is inadequate to describe the complete function of the genome, or the causation of disease.

Chapter Seven, Instinct

This chapter discusses whether the form and existence of language has a genetic component. Specifically, "specific language impairment" as possibly related to a gene on chromosome 7. Ridley discusses the scientific disagreement between Canadian linguist Myrna Gopnik and others regarding whether this disorder relates to difficulties with grammar formulation, or is more broad intellectual disorder. Genome, at page 104-05.

Chapter X and Y, Conflict

Ridley contemplates evolutionary psychology using the genes SRY (on the Y chromosome), DAX1 and Xq28 (on the X chromosome). The theory of genetic conflict and evolution is debated using the rhetorical question, are we bodies containing genes, or genes in bodies?

Chapter Eight, Self-Interest

Richard Dawkins' concept of the "selfish gene" is described by Ridley through a discussion of retrotransposons. This includes the behavior of the LINE-1 and Alu transposons. Further, Ridley discusses the possible purposes of cytosine methylation in development. The chapter also discusses how through reverse transcriptase retroviruses like HIV copies itself to the human genome.

Chapter Nine, Disease

For Chromosome 9, the book examines the discussion of the blood-typing genetic sequences. Namely, the ABO blood groups and their impact on evolution are discussed. Other genes mentioned include CFTR for cystic fibrosis. Ridley concludes that the Human Genome Project is largely based on the inaccurate belief that there is one single human genome. Proof that this is wrong comes from answering the question, which of the several choices of blood typing genetic sequence is selected, since each one has different disease-resistant and evolutionary consequences?

Chapter Ten, Stress

The impact of stress on the human body is described starting with the creation of hormones by the CYP17 gene on chromosome 10. Ridley points out the relationship between cholesterol, steroidal hormones such as progesterone, cortisol, aldosterone, testosterone and oestradiol.

Chapter Eleven, Personality

Ridley chooses the gene D4DR which codes for the manufacture of dopamine and is located on the short arm of chromosome 11. Interactions between dopamine, serotonin and other serotonin neurochemistry are lightly covered.

Chapter Twelve, Self-Assembly

This chapter relates to how understanding the genetic code matches models for embryonic development among vertebrates. Ridley discusses 'gap' genes, 'pair-rule' genes, and 'segment-polarity' genes. Homeotic genes and Hox genes are described briefly. Walter Gehring's discovery of the homeobox set of codes in 1983 is related to an on and off switch metaphorically.

Chapter Thirteen, Pre-History

Ridley describes the relationship between the development of Indo-European and other ancient root languages and the classical polymorphisms which map genetic frequencies in Eurasia. The interplay between the breast cancer genes BRCA2 on chromosome 13 and BRCA1 on chromosome 17 help to illustrate these larger concepts. Ridley also describes genetic studies of different types of peoples to isolate why people developed a mutation allowing adults to digest lactase in adulthood. He concludes that since the herding tribes of the world all evolved this mutation earliest, these people's genes adapted to their environment. In a twisted way, this perhaps sounds like the theories of Larmarck who suggested that the blacksmith's beefy strong arms were 'handed down' to his children directly - though it is actually quite different. The controversial conclusion is that willed action can alter our evolutionary history and genetic composition, by changing the environment to which we have to adapt.

Chapter Fourteen, Immortality

This chapter examines the so-called "immortality" of the genetic code - i.e. how is it that genetic code can remain as precise as it has been for 50 billion copyings since the dawn of life? Part of the answer is in the protein enzyme telomerase, lying on chromosome 14 and coded by the gene TEP1.

Chapter Fifteen, Sex

Ridley begins with two different “genetic diseases,” Prader-Willi syndrome and Angelman’s syndrome, both of which are caused by the lack of the same chunk of chromosome 15, and it has been shown that whether a child inherits one syndrome or the other depends on the parent from whom the mutation is inherited: Prader-Willi from the father, Angelman’s from the mother. This relates to sexual antagonism and the fact that the placenta is controlled by paternal genes in order to be “invasive enough” into the mother’s body and resources. Genetic cloning, like the case of Dolly, seems to erase all genetic “imprints” so the organism still survives. Imprinting has an effect on the brain too, in that the mother’s genes control the development of the cerebral cortex while the father’s control the development of the hypothalamus, so essentially we inherit our mother’s way of thinking and our father’s innate moods. Accordingly, gender roles in behavior have also been shown to be controlled by the genome rather than by environmental situations around an individual.^[1]

Chapter Sixteen, Memory

Ridley introduces the problem of knowledge versus instinct, and learning versus heritability, but then asserts that natural selection will make universal common knowledge like grammar instinct but will leave things like vocabulary to be learned so that it can change with time. Eric Kandel isolated a chemical called cyclic AMP, a chemical found in neurons, that is involved in the process of learning by changing itself when something is learned. It has also been shown without a doubt that humans are not the only creatures capable of learning. Bees, mice, and even sea slugs can learn, as proven by Kandel’s study and many others. However, while the human brain is capable of immense amounts of learning, the brain is created and ultimately controlled by genes and related proteins and chemicals.

Chapter Seventeen, Death

The chapter focuses on cancer, and introduces it with the principle that cells occasionally reproduce themselves when they are not supposed to. Cancer is when they are not stopped from doing so. A gene called TP53, on the short arm of chromosome 17, is responsible for suppressing rogue cancer cells, and is classified as a tumor-suppressor gene. These genes are the opposite of oncogenes, which are genes that encourage cell growth. Therefore, oncogenes can cause cancer when they are kept switched on, but tumor-suppressor genes can also cause cancer when they are kept switched off. Ridley explains that the reason detecting cancer early is so important is that the more it progresses and the more the cells divide, the more mutations accumulate, which means the progression of the disease actually accelerates with time. Some cancer victims also carry mutations in “mutator genes” such as BRCA1 and BRCA2, in the case of breast cancer. The protein that TP53 produces called p53, which is in clinical trial as a cancer drug, acts as a police officer in cells that begin to duplicate themselves excessively by either halting cell division or by instructing the cell to commit suicide by a process called apoptosis. Ridley explains that in various types of cancers TP53 is mutated very early, which explains why chemotherapy and radiation therapy does not always work effectively in later stages of the disease (chemo and radiation help the body to help itself by damaging DNA which thereby “alerts” p53, but if the gene is mutated this cannot happen). I have attached a quote from page 240 that I found particularly inspiring about “reductionist” cancer research.

Chapter Eighteen, Cures

The chapter is about genetic manipulation, and the first example Ridley gives is in 1972 Paul Berg made the first man-made “recombinant” DNA by using restriction enzymes and ligase. Since then, there have been several experiments using recombinant DNA where a retrovirus would be stripped of its infectious genes and replaced with a desired gene and then injected into the body either directly or through cultured cell, trying to cure various diseases through gene therapy such as SCID, hemophilia, cystic fibrosis, and cancer. Genetic engineering has very unnecessarily polarized its proponents and radical environmentalists, stemming from the issue of agricultural genetic engineering. Ridley reviews the possibilities of human cloning with genetic improvement through the use of embryonic stem cells and recombinant DNA.

Chapter Nineteen, Prevention

Ridley introduces the chapter with a discussion of diseases that previously had no cure but now do, and that it is our moral obligation to treat and prevent those diseases when the knowledge to do so becomes available, specifically Alzheimer’s disease and coronary heart disease. He explains the process by which coronary heart disease develops and integrates the APO genes, specifically APOE, which help control the metabolism of fats and cholesterol, and explains that genetic testing could help doctors to suggest healthy eating and exercise habits depending on an individual’s APO genes. Alzheimer’s disease also has a strong connection with APOE, specifically the E4 allele, in that it somehow contributes to the characteristic plaque buildup in the brain cells. Ridley again discusses the issue of genetic testing of patients for an incurable disease such as Alzheimer’s and the associated but unfounded fatalism conveyed to the patient, although unlike Huntington’s disease it is not exactly fatalism because of other environmental factors and that even E4/E4 individuals can live long lives with no symptoms other than neuronal plaque buildup. He suggests that doctors will begin to use genetic tests in everyday diagnoses and prescriptions, but also discusses the negative effects of releasing genetic information to insurance companies and/or the government. “[Your genetic code] is yours, not the government’s, and you should always remember that.”

Chapter Twenty, Politics

The chapter’s theme is mystery, and it begins with the story of “scrapie,” a degenerative brain disease found in genetically engineered sheep that seemed to be infectious, but no “microbe” could be found. A similar disease was found among people in Papua New Guinea called kuru that had connections to a cannibalistic ritual. Another similar disease called CJD became an epidemic called iatrogenic CJD, meaning CJD caused by doctors, due to the presence of the disease on surgical materials even after sterilization. In 1982 Stanley Prusiner eventually isolated the gene, PRP, which produces a protein called a prion, which can suddenly change itself into an indestructible sticky lump that sticks together with other prions; they can also recruit other normal prions to the aggregate lumps. Therefore the scrapie disease could be both genetic and transmitted. Ridley discusses governments’ ridiculous methods of dealing with scrapie scares such as restricting consumption of beef and other animals.

Chapter Twenty-One, Eugenics

Ridley begins discussing eugenics with its definition and how it came about as more of a science-ized political creed rather than a politicized science. He begins with a political discussion of American eugenic beliefs stemming from anti-immigration and the fear of diluting the Anglo-Saxon American race. Even the Supreme Court began to allow sterilization, or the prevention of individuals from breeding, in 1927. Ridley also recounts the history of how Britain never passed laws allowing sterilization (not to say that doctors and hospitals never practiced it independently). In today’s world, although sterilization is considered inhumane and a direct violation of civil liberties, eugenics still happens every day in hospitals, especially to those individuals with trisomy 21, the genetic condition leading to Down syndrome. Genetic counseling is also partly based on the principle of eugenics. China is one of the few countries that still encourages eugenics and sterilization, and Ridley says that this is because the culture demands that the good of the society is placed before the good of the individual.

Chapter Twenty-Two, Free Will

Ridley blends the two factions of genetic determinism and freedom, saying that the notion that behavior is controlled by one’s environment is just as deterministic as that of genetic determinism. To say that a child abuser acts the way they do because they were abused as a child is just as deterministic and even more prejudicial. Ridley asserts that children actually have more nurture effect on their parents than parents do on their children, because children tend to shape themselves in accordance with their genes and their peers and tend to keep home life separate from the outside world. “Human behavior is therefore unpredictable in the short term, but broadly predictable in the long term” (312). One may choose not to eat lunch one day, but over time one will eat regularly. In the beginning of the chapter Ridley talked about a made-up gene called HFW in order to illustrate the difference between something being controlled by a gene and something innate to each of us, controlled by infinitely many factors including free will, which stems from oneself.

See also

• Genes VI, Benjamin Lewis (Oxford University Press, 1997)
• Human molecular genetics, Tom Strachan and Andrew Read (BIOS Scientific Publishers, 1996)
• Basic Genetics, Robert Weaver and Philip Hedrick (William C. Brown, 1995)
• DNA science, David Micklos and Greg Freyer (Cold Spring Harbor Laboratory Press, 1990)

References

External links

• Weizmann Institute, website of 'gene-cards' relating to each gene
• OMIM, Online Mendelian Inheritance in Man, Victor McKusick/National Library of Medicine/National Center for Biotechnology Information/McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine
• Hereditary Disease Foundation, Bio of Alice Wexler, author