Human Heredity and Ethical Problems

HUMAN HEREDITY AND ETHICAL PROBLEMS* BENTLEY GLASSf The discoveries of molecular biology and genetics during the past twenty years are now generally acclaimed to be the most significant basic scientific advances of our present generation, just as the understanding of the forces of nuclear energy in the atom was that of the preceding generation. Like the application of nuclear energy to both destructive and constructive purposes, the application of the spectacular finding that deoxyribonucleic acid (DNA) is the chemical basis of heredity offers man a magnificent extension of power over nature and at the same time lays on his conscience a frightening responsibility in the use of that power. Within these past twenty years it has been demonstrated conclusively how the DNA of the cell replicates and how errors in replication , errors producible either by high-energy radiations or by certain chemical agents, give rise to mutations, that is, produce permanent hereditary changes most of which are detrimental. Next was discovered the way in which the genetic code which is formed by the sequence of nucleotides in the DNA molecule is transcribed to ribonucleic acid (RNA), and the way in which the messenger molecules of RNA, after migrating from the nucleus of the cell to the cytoplasm , are transcribed on the ribosomes into specific sequences of amino acids in a polypeptide molecule. The problem of protein synthesis , which lies at the basis of all formation of living structures and all control over living processes, has been clarified beyond wildest expectations. The "one gene-one enzyme" hypothesis has become the well-established "one gene (or cistron)-one polypeptide" theory, and is transformed into doctrine or dogma, so quickly has it become a basic concept of biology. * First annual address to the Society for Health and Human Values, October 29, 1970, Los Angeles. t Academic vice-president and Distinguished Professor of Biology, the State University of New York at Stony Brook, New York 11790. Present address: 517 Meder Street, Santa Cruz, California 95060. Perspectives in Biology and Medicine · Winter 1972 | 237 The genetic code itself, relating each triplet codon of the messenger RNA to the insertion into the polypeptide of a specific amino acid, has been established in full detail and has been shown to be as universal a language of life as the very existence of life itself, from the simplest virus to the most complex of beings. Knowledge of the way in which specific protein syntheses are turned on and off during metabolism, and especially during the differentiation of cells and tissues during a multicellular organism's development, has advanced from the stage of theory to that of actual isolation of repressor molecules which are elaborated by the regulatory genes that keep a cluster of related genes in a chromosome turned off until the moment when needed. Twenty different kinds of transfer RNA molecules have been isolated , each one of which serves to convey to the appropriate site of protein synthesis a particular sort of amino acid, and each of which corresponds by possession of an anticodon to a particular codon of the messenger RNA, so that it fits perfectly into the coded sequence. In 1964 RobertW. Holley completely analyzed one of these transfer RNA molecules into its sequence of seventy-seven nucleotides, and in 1970, just six years later, Ghobind Khorana performed the feat of chemically synthesizing this gene. Meanwhile, Beckwith and his colleagues at Harvard have isolated in pure form one of the genes of the lactose operon in Escherichia coli. Thus, rapidly, yet step by step, the way has been opened to producing a great variety of genes which might be introduced into living cells in order to supply various hereditary deficiencies. Maybe by using a harmless virus as a carrier for such genes, in the manner known to geneticists as transduction, genes can be introduced into the particular organs where they are needed, and can be made a part of the regular replicating genome of the cell. Or perhaps, like the original classical transformation experiments of Avery, MacLeod, and McCarty with pneumococcus in the 1940s, treatment of deficient cells and organs with the isolated or synthesized active genes will become feasible. In either case, what Joshua...