Reviewing a science book for high-school honors courses

Essential Genetics
Second edition, 1999. 552 pages. ISBN: 0-7637-0838-0.
Jones and Bartlett Publishers, 40 Tall Pine Drive, Sudbury, Massachusetts 01776.

I Am Pleased to Endorse This Excellent Book

David L. Jameson

Now we have one: the second edition of Essential Genetics, by Daniel L. Hartl and Elizabeth W. Jones. Like Essential Cell Biology, this new book is appropriate for bright high-school students, provided that they have already taken basic high-school courses in both biology and chemistry.

The authors of Essential Genetics are first-rate scientists: Hartl is a professor of biology at Harvard, Jones a professor of biological sciences at Carnegie Mellon University. Their book is distinguished by tersely written text and by fine illustrations that support the teaching of the subject matter. None of illustrations in Essential Genetics is pretty padding. Each has a story to tell, and each tells its story well.

The book's fourteen chapters include four that deal with Mendelian principles, two that deal with the structure, replication and mutation of DNA, two that address molecular genetics, and two that cover population genetics and evolutionary genetics. Single chapters are devoted to prokaryote genetics, recombinant DNA, gene regulation, and the control of development. The authors integrate classical, molecular, and evolutionary genetics in refreshing, thoughtful presentations that show how today's geneticists think, work and hypothesize.

The principle that genes interact with environments is introduced early. On page 21 the student learns about phenylketonuria (PKU) and about the link between maternal PKU and fetal health. (PKU is a hereditary disease in which the metabolism of phenylalanine, an amino acid, is deranged. If a woman afflicted with PKU becomes pregnant, the phenylalanine in her diet can adversely affect the development of the fetus that she is carrying, even if the fetus itself is not phenylketonuric and is able to metabolize phenylalanine in the normal way.) This is a stimulating example of the importance of genetic knowledge to human welfare.

Hartl and Jones offer many other examples as well, presenting some of them in feature articles marked "The Human Connection." These articles reproduce excerpts from original reports in the scientific literature. For instance:

• In the "Human Connection" article on page 50 we read passages from Karl Landsteiner's paper "On Agglutination Phenomena in Normal Blood," published in 1901. That is the paper in which Landsteiner reported his discovery of the ABO blood-group system -- a discovery that enabled physicians and surgeons to turn blood transfusion into a safe, reliable medical technique.

• The "Human Connection" article on 478 offers excerpts from Anthony C. Allison's 1954 paper on sickle-cell anemia. We read about some of his observations, then his canny conclusion that the sickle-cell allele is maintained at high frequencies in some African populations because sickled red cells resist invasion by Plasmodium falciparum, a parasite which causes malaria: "Hence those who are heterozygous for the sickle-cell gene will have a selective advantage in regions where malaria is hyperendemic." (Suggestion: Ask your students to investigate how this advantage varies geographically. In some places where malaria is prevalent, an unpaired sickle-cell gene is markedly beneficial, but in other places the benefit is much less pronounced.)

• The article on page 133 focuses on the classic paper in which Joe Hin Tijo and Albert Levan, in 1956, answered an ostensibly simple question: How many chromosomes are there in a diploid cell of a human? In fact, the question wasn't simple, because finding and separating all the chromosomes in a human nucleus was difficult. During the first half of this century, biologists universally and adamantly insisted that the diploid number was 48. Tijo and Levan devised an improved technique for separating chromosomes and, in observations of 261 embryonic cells, found that "the chromosome number 46 predominated" and was not exceeded. "We do not wish to generalize our present findings into a statement that the chromosome number of human beings is 2n = 46," they wrote, "but it is hard to avoid the conclusion that this would be the most natural explanation of our data." That memorable understatement, hard to beat as an example of sober science writing, seems worthy of considerable discussion in the classroom.

Genetics is permeated by chromosome counts and other numbers, and by equations that help us understand what the numbers mean. Hartl and Jones slip these in nicely, using nothing more than simple algebra and some concepts of probability (which are explained well).

On page 105 the authors discuss the question of whether Mendel fudged his data. They tell some reasons why the statistician Ronald Fisher, in 1936, declared that Mendel's reported results were too good to be true; then they suggest that Mendel may have "discarded or repeated a few experiments with large deviations that made him suspect that the results were not to be trusted"; and then they quote Sewall Wright's conclusion that "Taking everything into account, I am confident that there was no deliberate effort at falsification." This discussion discloses differences between our modern knowledge of probability and the knowledge that prevailed in Mendel's time. It also demonstrates some differences in temperament between Fisher and Wright, two of the great thinkers of genetics.

If Mendel really discarded some of his results because they seemed bizarre or unreliable, he wasn't the last person to do so. Sometimes, genetic investigations depend on a sort of informed intuition about what to count and what to ignore. Such intuition was important in the research that led to the discovery -- by Jerome Lejeune, Marthe Gautier and Raymond Turpin -- that Down syndrome is attributable to the presence of an extra chromosome. You'll find a description of that research on page 178 of Essential Genetics, with excerpts from Lejeune, Gautier and Turpin's 1959 paper "Study of the Somatic Chromosomes of Nine Down Syndrome Children."

I have had to look hard at Essential Genetics to find something with which I can disagree. Here it is: On page 82, Hartl and Jones make the dramatic claim that "The Human Genome Project is the first large scientific undertaking to address the ethical, legal, and social implications (ELSI) that may arise from the project." How about the Manhattan Project and other nuclear-weapons programs? While the Manhattan Project, for obvious reasons, didn't include any public examination of its societal implications, I must point out that nuclear scientists and technologists have been conducting such an examination continually, in The Bulletin of the Atomic Scientists, for the past 60 years.

Jones and Bartlett, the company that publishes Essential Genetics, has augmented the book with various accessories, including CD-ROMs for the student, an array of Web sites that provide end-of-chapter exercises, and a "ToolKit" CD-ROM for the instructor. I have looked at some of the Web sites and have found that the exercises are appropriate to their respective chapters. However, many high-school students still don't have access to the Internet in their homes, so they can't readily use the Internet in performing homework assignments or in preparing for tests. I find it difficult to support reliance upon the Internet unless teachers are able to ensure that all of their students have fair access to Internet resources.

Essential Genetics will provide stimulation, learning, and just plain fun for students and teachers alike. I am pleased to endorse it, both as a reference book for teachers and as a textbook for use in high-school honors courses and AP courses.

David L. Jameson is a senior research fellow of the Osher Laboratory of Molecular Systematics at the California Academy of Sciences. He has written books about evolutionary genetics and the genetics of speciation, and he is a coauthor of a college-level general-biology text.

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