Maxine Frank Singer was a researcher who studied molecular biology and genetics in the United States during the twentieth and twenty-first centuries. Her work synthesizing RNA molecules advanced researchers’ ability to understand triplets of nucleotides in RNA and DNA, which allowed them to read the genetic code. Singer was also one of the first scientists to find that certain long repeated DNA sequences, called long interspersed nucleotide elements, or LINEs, can jump around, and the mechanism behind it. Outside of her research, Singer also was active in science policy, helping to regulate the use of genetic engineering and recombinant DNA technologies, and organizing conferences around the topic, such as the Asilomar Conference. Prior to Singer’s work, researchers knew that DNA was a double stranded molecule made up of alternating nucleotides, but Singer contributed to researchers’ understanding of what those nucleotides meant in the genetic code. While Singer advanced the scientific community’s understanding of how to read the genetic code and how LINEs impact genetic diseases, her promotion of ethical discussions of scientific responsibilities in manipulating the code helped create policy that continues to affect researchers exploring genetic engineering as of 2024.

Heinrich Hermann Robert Koch was a researcher from Germany who studied the causative agents of infectious diseases in various parts of Europe, Africa, and Asia during the late nineteenth and early twentieth centuries. Koch developed what researchers call Koch’s postulates, which are four criteria designed to establish whether a bacterium causes a certain disease, and as of 2025, many researchers still use Koch’s postulates to guide their research. He also received the Nobel Prize in Physiology or Medicine for his discovery of Mycobacterium tuberculosis, which is the bacterium responsible for tuberculosis, an infectious disease that primarily attacks the lungs. Koch’s research on identifying disease-causing bacteria for various infectious diseases has advanced disease prevention and treatment, especially for tuberculosis, which has the ability to transmit from mother to child.

Lewis Madison Terman was a researcher and university professor who studied educational psychology and advocated for eugenics in the United States during the early twentieth century. The US eugenics movement, which Terman supported, was a collection of scientific research and social programs that aimed to improve human populations through control over human reproduction. One area many eugenicists studied was human intelligence as a means of determining how “desirable” a person may be. During the 1910s, while working at Stanford University in Palo Alto, California, Terman helped devise the Stanford-Binet scale for intelligence testing. As of 2024, the Stanford-Binet test is one of the main methods for providing individual intelligence quotient, or IQ, scores. In addition to the Stanford-Binet scale, Terman promoted the idea that individuals had fixed and inherited capacities for intelligence. Through both his development of a widely used method for measuring human intelligence and his promotion of the idea of intelligence as hereditary, Terman supported widespread social efforts to control human reproduction in the US during the twentieth century.