Reviewed by: Heredity under the Microscope: Chromosomes and the Study of the Human Genome by Soraya de Chadarevian Miguel García-Sancho Soraya de Chadarevian. Heredity under the Microscope: Chromosomes and the Study of the Human Genome. Chicago: University of Chicago Press, 2020. 272 pp. Ill. $37.50 (978-0-226-68511-3). In Heredity under the Microscope, Soraya de Chadarevian complements the picture of post-World War II biomedicine that she uncovered in her previous book, Designs for Life: Molecular Biology after World War II.1 Unlike in her earlier monograph, here she focuses on chromosomes as spaces of convergence of several lines of inquiry. This focus on research objects rather than disciplinary developments leads her to investigate a variety of practices that life scientists deployed to visualize and [End Page 466] interpret human chromosomes. The diversity of disciplinary backgrounds of these scientists and the multiplicity of uses to which their chromosome practices were put enable the author to expand the historiographical boundaries of both molecular biology and genetics research. Firstly, de Chadarevian disentangles “the study of postwar human heredity from the predominant concern about continuities with eugenic practices” (p. 5). The book does not limit itself to documenting the invention of karyotyping techniques to represent and detect anomalies in human chromosomes; it follows their standardization and spread, including their use as evidence of safe levels of radiation in the workplace (chapter 1) or sex assignment in the Olympic games (chapter 3). The emphasis on these uses, departed as they were from scientific theories about population improvement, displaces eugenics as the dominant interpretative framework of the history of human genetics. Secondly, the book presents chromosomes as showing “historical commonalities” (p. 177) between two approaches that have been traditionally considered as separate: molecular genetics and microscope-assisted chromosome observations. De Chadarevian stresses how these two approaches emerged as a consequence of the key role that nuclear research had played during World War II and the search of peacetime applications. Radioactive isotopes decisively fostered molecular biology, while the investigation of the effects of radiation was a crucial concern of human and medical geneticists using chromosome observations (chapter 1). Both molecular biologists and chromosome researchers also attempted to apply computers to their investigations, the former as an aid to the structural study of proteins and DNA, and the latter to automate the interpretation of karyotype images (chapter 4). However, whereas molecular biologists focused on simpler organisms, chromosome researchers engaged with both human populations and patients in the clinic. Radiation-induced leukemia was their first focus for then rapidly shifting to other conditions (especially those affecting mental abilities and sex identity) and larger-scale epidemiological studies (chapters 2 and 4). The 1960s, a decade that historians have dubbed the golden age of molecular biology,2 was also a time of expansion of chromosome observations. From the mid-1970s onward, molecular biologists turned to human subjects in order to realize the medical promise of the new recombinant DNA techniques. It is at this point when the intersection with chromosome research becomes more visible and de Chadarevian wonders “whose turn” this represents in history, a molecularization of human genetics or a humanization of molecular biology (pp. 171–76). Although subsequent success stories have put the emphasis on molecular biology, chapter 5 shows the importance of chromosome research as a key tool for gene mapping and the emergence of the human genome as an object of study. Even in the so-called post-genomic era, chromosome observations are [End Page 467] essential to clinically interpret the molecular sequence data derived from the Human Genome Project. Overall, the book offers a most welcomed framework to address the coexistence of chromosome observations and molecular biology, and their importance in genomics research. Understanding this is a pressing historiographical problem, given the dominance of molecular biologists in existing narratives and the apparent revival of chromosome research. There is yet still work to do in exploring specific overlaps between the visual and molecular approaches to the genome. A potential candidate is Victor McKusick, a main actor in de Chadarevian’s account and a co-author of the article in which Celera Genomics presented one of the draft sequences of the human...
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May 28, 2023
Jonathan Marks 
Open Access