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DNA: A Graphic Guide to the Molecule that Shook the World

DNA: A Graphic Guide to the Molecule that Shook the World

Israel Rosenfield
Edward Ziff
Borin Van Loon
Copyright Date: 2011
Pages: 272
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  • Book Info
    DNA: A Graphic Guide to the Molecule that Shook the World
    Book Description:

    With humor, depth, and philosophical and historical insight, DNA reaches out to a wide range of readers with its graphic portrayal of a complicated science. Suitable for use in and out of the classroom, this volume covers DNA's many marvels, from its original discovery in 1869 to early-twentieth-century debates on the mechanisms of inheritance and the deeper nature of life's evolution and variety.

    Even readers who lack a background in science and philosophy will learn a tremendous amount from this engaging narrative. The book elucidates DNA's relationship to health and the cause and cure of disease. It also covers the creation of new life forms, nanomachines, and perspectives on crime detection, and considers the philosophical sources of classical Darwinian theory and recent, radical changes in the understanding of evolution itself. Already these developments have profoundly affected our notions about living things. Borin Van Loon's humorous illustrations recount the contributions of Gregor Mendel, Frederick Griffith, James Watson, and Francis Crick, among other biologists, scientists, and researchers, and vividly depict the modern controversies surrounding the Human Genome Project and cloning.

    eISBN: 978-0-231-51231-2
    Subjects: Biological Sciences, Ecology & Evolutionary Biology

Table of Contents

  1. Front Matter
    (pp. i-viii)
  2. Table of Contents
    (pp. ix-x)
  3. Preface
    (pp. xi-xiv)
    Israel Rosenfield, Edward Ziff and Borin Van Loon
  4. Introduction
    (pp. 1-4)

    In December of 1949, almost four years before James Watson and Francis Crick published their model of DNA, launching the revolution in modern biology, the mathematician and designer of the computer, John von Neumann, gave a lecture explaining how a machine could reproduce. All it needs, he said, is a description of itself.

    A machine with a magnetic core could not reproduce the magnetic core by making a mold. However, if it had a description reading, “magnetic core: electric wire tightly wound around metal bar five hundred times, etc.” and it had the necessary raw materials, it could easily follow...

    (pp. 5-27)

    By the 1860’s most biologists accepted the view that all plants and animals consisted of cells. It was known that cells give rise to new cells through cell division.

    Yet, nobody could explain how cells divided.

    DNA was discovered in 1869 by Frederick Miescher, who was then 25 years old.

    Miescher was the son of a well-known physician in Basel. In 1869 he had gone to Tubingen to study the chemistry of white blood cells with the biochemist F. Hoppe-Seyler. He used pus obtained from postoperative bandages, as a source of the cells. When he added weak hydrochloric acid to...

    (pp. 28-33)

    DNA is like a long string of beads in which each bead can be one of four kinds. Information is coded in the order in which the beads are arranged on the string. The untied part of each bead is known as a “base” and has a name: adenine, guanine, cytosine, or thymine. (In RNA, whose function we will study later, thymine is replaced by uracil.) By 1900 all of these bases were known to chemists, and were classified into two groups: the purines, adenine and guanine; and the pyrimidines, cytosine, thymine, and uracil. These are abbreviated A, G, C,...

    (pp. 34-57)

    The immediate question was how DNA could be informational. Erwin Chargaff, a young Viennese-trained chemist, unlocked the first chemical clues to genetic information storage in DNA. Chargaff read the Avery, MacLeod, and McCarty paper on the transforming principle.

    Chargaff’s approach was to use the methods of quantitative analysis, bolstered by newly available techniques for separating the four bases. He purified DNA samples and then carefully quantified the amount of the four bases, A, G, C, and T.

    When Chargaff measured the base compositions of DNA from many sources he noted regularities summarized in “Chargaff’s Rules”:

    This chemical symmetry was at...

  8. DNA Replication
    (pp. 58-59)

    Watson & Crick’s model of DNA suggested the mechanism of replication.

    We now know that DNA synthesis begins at a Replication Origin.

    One enzyme unwinds the double helix at the origin, forming a Replication Fork.

    At the fork the two separated strands serve as templates for new DNA synthesis.

    Here are more enzymes called DNA polymerase – they travel along the strands catalyzing the addition of DNA nucleotides... create two double strands.

    Since adenine always pairs with thymine, & cytosine always pairs with guanine (the four bases), each new chain will be complementary to the parent chain that it uses as...

    (pp. 60-66)

    Replication is an extremely complicated process, but this guarantees the near perfect accuracy of genetic transmission & consequently, life itself!

    As we have seen George Beadle & Edward Tatum proposed:

    The critical clue to the complexity of this genetic information came from Fred Sanger, an English biochemist, who determined the complete amino acid sequence of the hormone insulin.

    Insulin is a protein. Proteins are long chains of amino acids. There are twenty amino acid types.

    Sanger proved that proteins have specific structures. This had implications for genes.

    Sanger sequenced insulin by specifically degrading it into short fragments which were seperated by a...

    (pp. 67-69)

    Remember Zamecnik? He found...

    How did the coded information get from the cell’s DNA to the ribosome?

    It was only after Arthur Pardee, François Jacob & Jacques Monod working together at the Pasteur Institute in Paris performed their famous “PaJaMo” experiments (named after themselves), that this piece of the puzzle fell into place.

    The gene for making an enzyme, beta-galactosidase (which digested the sugar lactose), were transferred from the male bacteria to the females which were not capable of making the enzyme.

    (As we shall see later, bacteria have “sex.”)

    The gene for beta-galactosidase no sooner entered the female than it...

    (pp. 70-74)

    How is the information coded on a DNA strand used as a template for manufacturing proteins?

    Here’s RNA polymerase which we can think of as a mobile scanner.

    It’s crucial to the process of transcription (the copying of the DNA code into messenger RNA)–

    –so crucial, in fact, that when a gene or two needs to be transcribed the driver rushes into action!...

    The mobile scanner senses the Promoter on the DNA and rolls into position on the Initiation Site, causing the strands to unwind!!... it rolls forward over the strand to be transcribed.

    We can imagine this occurring...

    (pp. 75-84)

    We will see later that the genes & mRNA of the cells of eukaryotes – such as plants and animals (cells with nuclei) – are more complex.

    In the cells of prokaryotes – such as bacteria (that is cells without nuclei) – an mRNA can hold the codes for a number genes:

    Let’s take a closer look...

    The ribosome is a microscopic particle which acts as the cell’s protein factory & is made of protein & RNA. It has two parts:... small large

    Its job is to manufacture proteins using the coded RNA messenger train.

    The 5’end of the train arrives...

  13. Genetic Code
    (pp. 85-87)

    The “genetic code” itself was cracked in the early 1960’s. Severo Ochoa of the New York University Medical School devised enzymatic methods for making RNA molecules in the test tube which had defined nucleotide sequences.

    Marshall Nirenberg and his student Phil Leder, working at the National Institutes of Health in Maryland, used synthetic RNA made by Ochoa’s methods to direct protein synthesis by cell extracts in the test tube.

    They found that simple RNA trinucleotides, the minimal molecules for specifying a code word, were sufficient for binding tRNA to ribosomes. The RNA triplet would bind to the ribosome, and guide...

    (pp. 88-94)

    What’s the genetic origin of these features?...............

    A bacterium with DNA inside...

    ...(made of some of the 4 million DNA base trucks)...

    ...DNA holds the coded genetic information...

    ···as we have seen, the coded Information is transcribed by RNA polymerase – the mobile scanner.

    What determines whether digestive enyzme & permease are manufactured?

    We’ll call the sugar the inducer as it’s only when it’s present that (in the ‘normal’ bacterium) the repressor does not function & the manufacture of these little machines is induced.

    The result: sugar induces the enzymes required for its uptake & digestion!

    The Operon model disclosed by PaJaMo ranks...

    (pp. 95-101)

    Mutation is one source of gene diversity.

    But life on earth began some 3 to 4 billion years ago.

    If the only cause of variation was random mutation, evolution would have been very slow!

    Sexual reproduction could have provided great variability in primitive organisms by reshuffling mutations. But can primitive organisms like bacteria have sex?

    Well, Joshua Lederberg at 19 wondered about just that.

    Lederberg took two strains of bacteria. Each needed two nutrients to grow, A & B for one, C & D for the other.

    He put the two strains together in a growing medium locking all four nutrients.


    (pp. 102-103)

    After about twenty minutes, hundreds of replicas of the original phage are assembled and burst out of the bacterium, ready to find other bacteria & start the cycle again!

    The E. coli bacterium (found in the human intestine) is just over a thousandth of a millimeter long!

    To bring E. coli up to the size of a bean, it would need to be magnified 30,000 times, yet it can hold hundreds of phage!

    The small circle of DNA called a plasmid which can be absorbed by the bacterium is about one thousandth of a millimeter long!

    Flabbergasted? Let’s further confound you...

    (pp. 104-104)

    Sperm are made in the testes and ejaculated through the man’s penis (hundreds of millions of sperm in one ejaculation!!)

    Eggs are stored in the woman’s ovaries & released at the rate of one every four weeks; they lodge in the fallopian tubes awaiting fertilization by one of the sperm.

    A single sperm cell (at the head of the lashing tail) is mainly made up of nucleus.

    The egg cell (smaller than a pinhead) has jelly-like cytoplasm enclosing a nucleus.

    Inside the nucleus is a darker-staining material known as chromatin made up of fine tangled threads.

    Now, when a cell is...

  18. Prokaryotes versus Eukaryotes
    (pp. 105-113)

    With the genetic code cracked, and the outlines of genetic regulation firmly established for bacteria and their viruses, scientists began to confront the awesome problem of gene structure and regulation in higher eukaryotes (those having cells with nuclei) including man.

    Some dismissed the problem altogether saying:

    Others argued that:

    In eukaryotes, because the DNA is contained in the nucleus, it is in a compartment isolated from the translation machinery, which resides in the cytoplasm.

    Bacteria, because they lack nuclei, carry out transcription and translation side by side.

    Most bacteria contain approximately ten million nucleotides which we have drawn as single...

  19. Restriction Enzymes and Genetic Engineering
    (pp. 114-123)

    In 1970, Ham Smith and co-workers at Johns Hopkins University found that extracts of the bacterium Haemophilus influenzae cut DNA into very specific pieces.

    One enzyme from this bacterium, Hindll enzyme (as it was later called), recognizes a six-base sequence, GTYRAC (where R is A or G, Y is T or C) and cuts the two DNA strands within this sequence at precisely opposing points in the helix.

    A second enzyme, isolated from E. coli and named EcoRI, recognizes a six-base sequence, GAATTC, but the strand cuts are displaced 4 nucleotides from one another. The ends made by HindII are...

    (pp. 124-135)

    All of the plasmids in one bacterial colony descend from a single “parent” plasmid – the one which originally entered the bacterium. They are all identical, and constitute a “clone.” A foreign DNA fragment amplified by insertion in a plasmid in this manner is said to be “cloned.” Cloning therefore can provide large quantities of a pure gene which normally exists only in minute quantities in the cell.

    Now that any gene may be made plentiful through cloning, how shall we study it? Most of the information content of a gene lies in the precise sequence of the nucleotides. Therefore,...

  21. Exons, Introns, and Splicing
    (pp. 136-142)

    Early surveys of eukaryotic DNA revealed that some DNA sequences were present only once per cell. However, others were present many times. Some of the highly repeated sequences were likely to have a structural rather than an informational role. The coding sequences of genes fell in the “unique sequence class.”

    Something was known about the RNA of animal cells, too. Like bacteria, animal cells had messenger RNA (the train carrying the coded information from RNA polymerase to the protein factory), ribosomal RNA (which makes up part of the protein factory), and transfer RNA (which carries amino acids to the protein...

    (pp. 143-143)

    Many genes are transcriptionally controlled.

    For some genes repressors or activators which bind to the promoter are likely to control transcription, just as in bacterial genes.

    However for many eukaryotic genes, the structure of the chromatin (dark-staining material inside the nucleus) may be critical and controlled by other proteins.

    Chromatin is a complex of eukaryotic DNA with positively charged proteins called histones.

    DNA winds twice about the core to form the fundamental subunit of chromatin called the nucleosome.

    The histones form a nucleosome core.

    Chromatin consists of many nucleosomes linked by DNA & packaged into more complex but regular fibers. The...

    (pp. 144-145)

    Different genes are expressed as cells differentiate.

    During development, different globin proteins are expressed: the embryonic, the fetal, and finally the adult globin. The developing organism’s requirements for transporting oxygen change as it grows from embryo to fetus to adult. Therefore different forms of the oxygen-carrying globin protein are produced through the successive activation of genes for:

    The genes for the different globin types are situated together within a 40,000-base region of the human genome. They form a gene family.

    Now let’s put the human globin genes into context with similar genes in other primates.

    Although embryonic, fetal, and adult...

  24. Controlling Genes for Antibodies
    (pp. 146-153)

    Some genes are controlled by unusual mechanisms, such as genes for antibodies.

    When the structure of DNA was first elucidated in 1953, it was believed that random mutations in the DNA structure and sexual recombination would account for evolution. Genes often exist in duplicate copies in an organism and the process of duplication allows for the creation of mutant structures – that may or may not help the organism adapt – without sacrificing the original gene.

    It was soon learned that there are mechanisms for rearranging DNA within a particular plant or animal. One of the most remarkable (and unusual)...

    (pp. 154-154)

    Each chromosome is a single double-stranded DNA, which in humans is a linear molecule. If fully stretched, the DNA of a typical chromosome would be about 2 yards in length.

    But by folding the DNA into chromatin, the chromosomes are only 20 millionths of a yard in length or less!

    Chromosomes have arms (chromatids) that are joined at the center by the centromere.

    While goldfish have 47 kinds of chromosomes per cell and dogs have 39, humans have 23 kinds, each present in two copies, except for X and Y in males, of which there are one each. The Y...

    (pp. 155-155)

    The DNA in chromosomes is one long, linear, double-stranded molecule. DNA polymerase replicates the majority of the DNA; however, it cannot complete the job. It has no trouble synthesizing one strand of the double helix (the “leading strand”), which is made continuously until the polymerase reaches the end of the strand. But the polymerase cannot finish the other strand, which is called the lagging strand. The lagging strand is made in many short segments, each started by an RNA “primer” (see page 58). When the last RNA primer is removed, the place where it was bound remains uncopied and thus...

  27. Imprinting and Micro RNAs: “Hidden” Layers of Gene Regulation
    (pp. 156-156)

    Imprinting. Some genes are expressed differently if inherited from mother or father. Chromosomes of eggs or sperm acquire a set of marks (either DNA methylation or histone acetylation; see page 157) indicating whether they are of maternal or paternal origin. These marks are erased when eggs and sperm are created in subsequent generations. After they fuse, as development proceeds, new DNA methylation marks are created.

    Micro RNA activity. In 1998 Andy Fire and Craig Mello studied how small RNAs block gene expression in the nematode worm.

    They had uncovered an unconventional mechanism of gene control by “RNA interference” (RNAi), in...

  28. Epigenetics
    (pp. 157-158)

    Epigenetics is the transmission, from one cell to its descendants, of genetic information not encoded in the sequences of nucleotides of the DNA.

    Epigenetic mechanisms include DNA methylation, imprinting and micro RNA activity. DNA methylation: a carbon atom with three hydrogens (CH₃, a methyl group) is added to one of the bases, usually a cytosine that lies next to a guanine in the DNA strand, a sequence written “CpG”:

    During replication of a DNA molecule with methyl C (MeC), a complementary CpG lacking the methyl groups is synthesized in the daughter strand. An enzyme, DNA methylase, adds the methyl group...

  29. PRIONS
    (pp. 159-160)

    The epigenetic changes we have been describing are the consequence of changing patterns of the switching on and off of genes; the sequence of the DNA is not altered even if the epigenetic changes can be passed from one generation to the next. There are also non-genetic forms of inheritance. Best known is the prion, a protein structure that does not contain DNA or RNA, and that is associated with a number of nervous disorders in cows (bovine spongiform encephalopathy – “mad cow” disease), sheep (scrapie), and humans (Creutzfeldt-Jakob disease).

    The disease, first noticed among the Fore people of New...

    (pp. 161-162)

    On June 26, 2000, President Clinton in Washington and Prime Minister Blair in London simultaneously announced the first draft of the Human Genome.

    The entire human genome was sequenced by the International Human Genome Sequencing Consortium: the NIH Human Genome Project headed by Francis Collins. It cost about $3 billion in public funds. Celera Genomics, headed by Craig Venter, sequenced the genome for about $300 million but Celera made extensive use of human genome structure that was in the public domain. The Human Genome Consortium reported its sequence on February 15, 2001, in the journal Nature and the Celera Genomics...

    (pp. 163-164)

    I have as many genes as you, and our genomes have greater than 95% similarity.

    Yes, but my genes give me: -speech and reason -opposable thumbs -walking upright -a larger brain, and more.

    Small differences between the genomes of humans and chimpanzees make a big difference in physical and mental characteristics. But the basis for the special human qualities is not known.

    The platypus, which is midway between reptile and mammal, has a novel genome. The platypus lays eggs and the newborn suck milk from the mother, albeit through the skin rather than from a nipple. The platypus genome is...

    (pp. 165-165)

    Biology entered the era of “high throughput” sequencing, and new “massively parallel” methods can now determine millions of nucleotides in a single analysis. This gave rise to the new sciences of genomics and proteomics, in which computers extract massive quantities of data about DNA and proteins from genome sequences. One goal is to sequence an entire human genome for $1000. Personalized whole genome sequencing will guide the treatments for heart disease and neurodegenerative diseases. New cancer drugs will treat specific cancer-prone genetic conditions, based on genome sequences, and soon, full genomic analysis may be an essential step in treatment of...

  33. SNPs
    (pp. 166-166)

    Scientists have developed novel gene-mapping tools that speed the process of finding the gene responsible for a genetic disease, or for comparing two individuals genetically or establishing an individual’s ancestral origins. One example involves the study of single nucleotide polymorphisms.

    Single nucleotide polymorphisms (SNPs, pronounced “snips”) are changes in single DNA residues of the genome that are fairly common. A change is considered a SNP if it is found in at least 1% of the population. Over two million SNPs have been identified and they are found on all chromosomes, throughout the human genome. SNPs are powerful tools for assessing...

  34. Manipulating the GENOME
    (pp. 167-170)

    Gene mutation can cause hereditary disease. Of the 20,000 to 25,000 human genes, mutations in about 1,800 genes have been linked to specific diseases. These diseases, many of which result from the mutation within a single gene, may eventually be treated using new “genetic medicines,” such as stem cells and novel DNA and RNA drugs consisting of short nucleic acid fragments. These novel drugs can control the activity or expression of genes by modifying the RNAs they encode, most often by modifying mRNAs. Genetic medicines also include DNA or RNA that is introduced into tissues to alter gene expression (see...

  35. Cloning the Organism – The History
    (pp. 171-172)

    In 1928, Hans Spemann performed the first ‘nuclear transfer’ experiment. Using a baby’s hair he eased the nucleus from the cell of an embryo and squeezed this nucleus into an enucleated cell from a younger embryo.

    An identical embryo was produced.

    An important question remained unanswered. Could an adult cell – a mature liver cell, heart muscle cell or a skin cell – be reprogrammed to develop into an entire organism? Could the genetic mechanism be ‘rewound’ to start all over again?

    In 1938 Spemann, who had become the director of the Kaiser Wilhelm Institute of Biology in Berlin, proposed...

    (pp. 173-173)
    (pp. 174-175)

    1) have not yet specialized their functions;

    2) retain the capacity to differentiate into specialized cell types;

    3) renew themselves;

    4) can be used to treat disease.

    Stem cells may make it possible to grow new organs and tissues in the laboratory and to replace tissues and organs that are diseased, such as in heart, kidney or liver failure.

    The rapid progress in stem cell research has also created a debate over the ethics of cloning. And new issues are likely to emerge, such as cloning of individuals or even the creation of variant life-forms....

    (pp. 176-176)

    in 2006, Kazutoshi Takahashi and Shinya Yamanaka working in Kyoto were able to get mature mouse cells to return (“revert”) to an embryonic state, opening the possibility of creating clones without gene transfer.

    The rapid progress in stem cell research has raised the possibility of generating new nerve cells, heart tissue, liver, bone or other organs to replace diseased or accidentally damaged tissues. Stem cells are also an essential part of contemporary research into the mechanisms of human development and disease....

    (pp. 177-179)

    In seeking to create animal models of human diseases, scientists have engineered genes that can be turned on or off by drugs such as tetracycline (tet). By studying mice in which the ras oncogene was turned on by tetracycline, Ron DePinho at Harvard discovered that this oncogene both starts tumors and keeps them growing. Tumors formed when tetracycline was included in the diet and the tumors regressed when it was removed.

    These results suggest that tumors might be treated by turning off specific oncogenes.

    Oncogenes arise from normal genes by mutation (ras, brca) or mutation plus overexpression (myc). Brca mutation...

    (pp. 180-181)

    DNA can be used to diagnose disease. Huntington’s disease is a progressive and incurable hereditary disease of the central nervous system. The first symptoms, uncontrolled movements, clumsiness, inability to concentrate and depression, usually appear when diseased individuals are in their 30s to 50s. The disease results from CAG triplet nucleotide repeats – which encode glutamines – in the DNA of the Huntingtin gene.

    A Huntingtin gene with fewer than 26 CAG repeats is normal, but if the number is large, greater than 39 repeats, the Huntingtin protein is toxic and fatal. The availability of a definitive diagnosis, determining triplet repeat...

  41. DNA and the Judicial System
    (pp. 182-184)

    DNA plays a central role in deciding guilt and innocence in courtrooms around the world. Human DNA contains short non-coding DNA sequences (9 to 80 bases long) that may be repeated up to thirty times, called Variable Number of Tandem Repeat (VNTR) sequences.

    VNTRs are found many thousands of times in human DNA, and can be detected in trace amounts of DNA such as from hair roots, or in biological fluids. DNA is collected with a swab, amplified by PCR (see page 185), and cut into small specific fragments using restriction enzymes (see page 114). The DNA fragments are applied...

  42. PCR
    (pp. 185-187)

    The polymerase chain reaction (PCR) replicates DNA outside a living organism. PCR’s inventor, Kary Mullis, described its great power: “Beginning with a single molecule of the genetic material DNA, the PCR can generate 100 billion similar molecules in an afternoon. The reaction is easy to execute. It requires no more than a test tube, a few simple reagents, and a source of heat.”

    The DNA fragment to be replicated is mixed with short DNA primers, complementary to the ends of the DNA to be replicated. A heat-stable DNA polymerase, which synthesizes DNA copies, and the nucleotide precursors to the DNA...

    (pp. 188-195)

    Cloning not only taught us much about gene structure, but also captured the public imagination - and later its fears. The first public debate over the benefits and hazards of genetic engineering came in 1973 when scientists active in gene research considered the implications of cloning for society.

    Biologists recognized that the most likely effect of reorganizing DNA would be to make it, simply stated, non-functional. Genes have evolved through eons of selection, mutational change and natural trial.

    However, concern remained that a novel recombinant could have undesirable properties. For example, a bacterium synthesizing insulin in the gut of a...

  44. Biotechnology
    (pp. 196-198)

    With public fears of genetic engineering receding, scientists considered applying cloning to biotechnology.

    Biotechnology is the commercialization of biology and genetics. It is the application of new genetic technology to practical medical and industrial problems. Biotechnology arose in San Francisco, not far from Silicon Valley, the birthplace of the transistor, micro-chip, and computer industries.

    The first projects were to transfer the genes for medically important proteins such as growth hormone or insulin to bacteria where these proteins might be cheaply produced in abundance.

    The giddy stage of investment passed and many ask how, realistically, biotechnology might profit society. Here are...

    (pp. 199-211)

    In the nineteenth century the Swedish physicist Gustav Arrhenius suggested the theory of panspermia.

    A few years ago, Leslie Orgel and Francis Crick resuscitated the theory:

    Crick and Orgel call their version of Arrhenius’ theory, directed panspermia.

    But what if life did begin on earth. How could it have started? In 1924 the Russian biochemist A. I. Oparin published a monograph (little noticed at the time):

    In the 1950’s, Harold C. Urey and Stanley L. Miller...

    Other experiments produced the five bases that make up DNA and RNA and the sugars found in living organisms. Recently, large amounts of organic...

    (pp. 212-212)

    Adaption is not like solving an engineering problem. The jet engine did not evolve from the combustion engine, but was built from scratch. Biological organisms must somehow incorporate what is already there into the new organism.

    François Jacob:

    Because the globin gene – discussed earlier – was duplicated, an extra copy was available for tinkering. Mutation and natural selection could then create globin diversity....

  47. Selfish Genes
    (pp. 213-217)

    In 1976 Richard Dawkins published his book The Selfish Gene, creating a considerable stir throughout the scientific and even philosophical communities. Dawkins argued that selection is at the gene level.

    The aim of a gene, he said, is to survive from one generation to the next and it uses the bodies of living organisms.

    Human beings are simply survival machines for DNA.

    Then in 1980 Francis Crick and Leslie Orgel presented the ultimate argument for self-centered molecules: selfish DNA. Some DNA exists, they said, not because of any benefits it might bring to an organism, but because that DNA is...

  48. Evolving Evolution – Sources of Darwinian Theory
    (pp. 218-219)

    DNA is a marvel that has transformed society. However, to understand the full impact of DNA, we must appreciate Darwinian theory and its sources. Charles Darwin wrote On the Origin of Species in 1859, the keystone of modern evolutionary theory. As the English theoretical biologist John Maynard Smith wrote, ”No other writer had such a profound effect on the way we see ourselves, and no other brought about so great an extension in the range of subjects which we regard as explicable by scientific theory.” As we shall see, Darwin argued that all existing organisms come from one or a...

  49. The Big Gene Bet of the Last Millennium (1999 A.D.)
    (pp. 220-232)

    The neo-Darwinian view appeared to be spectacularly confirmed when the double helix was discovered in 1953, showing how genes composed of DNA transmitted hereditary characteristics.

    Not only did the structure of DNA suggest a mechanism for gene replication, it also made apparent how variations arising from random changes were possible and could be inherited through changes in the base sequence of a gene. This idea of small random mutations in the base sequences of genes appeared to confirm Darwin’s view, already mentioned, that nature “can act only by short and slow steps. Hence, the canon Natura non facit saltum, nature...

  50. Epilogue to the First Edition
    (pp. 233-244)

    DNA is the thread which connects us with our most remote ancestors. If there were any interruption in the chain of the inheritance of genetic information, the “evolutionary value” of previous millennia would be lost. The coded genetic information in DNA is the outcome of mutation and environmental selection which together create the evolutionary process. This information could not be replaced.

    If we knew every detail of the structure of a cell, apart from DNA, the chemical constitution of the cytoplasm and nucleoplasm, the lipid content of the membranes, the amino acid sequence of every protein and the folding of...

    (pp. 245-256)
  52. Reading List
    (pp. 257-257)
  53. Back Matter
    (pp. 258-258)