Between 1957 and 1959, Arthur Pardee, Francois Jacob, and Jacques Monod conducted a set of experiments at the Pasteur Institute in Paris, France, that was later called the PaJaMa Experiments, a moniker derived from the researchers' last names. In these experiments, they described how genes of a species of single-celled bacteria, called Escherichia coli (E. coli), controlled the processes by which enzymes were produced in those bacteria. In 1959, the researchers published their results in a paper titled 'The Genetic Control and Cytoplasmic Expression of 'Inducibility' in the Synthesis of b-galactosidase by E. coli'. When they compared mutated strains of E. coli to a normal strain, Pardee, Jacob, and Monod identified the abnormal regulation processes and enzymes produced by the mutated genes. The results showed how enzymes break down the molecules that the bacteria ingested. The PaJaMas experiments uncovered some of the molecular mechanisms that regulate how some genes yield enzymes in many species.

Franklin William Stahl studied DNA replication, bacteriophages, and genetic recombination in the US during the mid-twentieth and early twenty-first centuries. With his colleague Matthew Meselson, Stahl performed an experiment called the Meselson-Stahl experiment, which provided evidence for a process called semi-conservative DNA replication. Semi-conservative replication is a process in which each strand of a parental DNA double helix serves as a template for newly replicated daughter strands, so that one parental strand is conserved in every daughter double helix. Those findings supported the Watson-Crick Model for DNA replication proposed in 1953 by James Watson and Francis Crick, convincing many biologists about DNA’s structure and replication in the 1950s. Stahl’s genetics research, especially that of DNA replication, showed researchers how genetic information is distributed within a cell and is passed down from cell to cell.

Curt Jacob Stern studied radiation and chromosomes in humans and fruit flies in the United States during the twentieth century. He researched the mechanisms of inheritance and of mitosis, or the process in which the chromosomes in the nucleus of a single cell, called the parent cell, split into identical sets and yield two cells, called daughter cells. Stern worked on the Drosophila melanogaster fruit fly, and he provided early evidence that chromosomes exchange genetic material during cellular reproduction. During World War II, he provided evidence for the harmful effects of radiation on developing organisms. That research showed that mutations can cause problems in developing fetuses and can lead to cancer. He helped explain how genetic material transmits from parent to progeny, and how it functions in developing organisms.

First manufactured in 1988 by Serono laboratories, recombinant gonadotropins are synthetic hormones that can stimulate egg production in women for use in fertility treatments. Recombinant gonadotropins are artificially created using recombinant DNA technology, a technology that joins together DNA from different organisms. In vertebrates, naturally-occurring gonadotropins regulate the growth and function of the gonads, known as testes in males and ovaries in females. Medical professionals can derive female gonadotropins from the urine of pregnant and post-menopausal women, often using it to facilitate in vitro fertilization, or IVF. With the rapid development of assisted reproductive technologies like IVF, demand for human-derived gonadotropins rose to a global yearly demand of 120 million liters of urine by the beginning of the twenty-first century, which resulted in a demand that could not be met by traditional technologies at that time. Therefore, researchers created recombinant gonadotropins to establish a safer and more consistent method of human gonadotropin collection that met the high demand for its use in fertility treatments.

In February 1975, leading biology researchers and lawyers participated in what became known as the Asilomar Conference, a meeting to discuss and recommend policy regarding novel recombinant DNA, or rDNA, technology. rDNA is DNA that scientists create in a lab by combining genetic material from two distinct sources. A group of researchers, including Paul Berg, Maxine F. Singer, and David Baltimore, organized the Asilomar Conference, which was held at the Asilomar Conference Grounds in Pacific Grove, California. The purpose was to discuss how to manage the risk of researchers unintentionally creating harmful or deadly pathogens through rDNA research. The conference resulted in the creation of the NIH Guidelines for Research Involving Recombinant DNA Molecules in 1976, which outlines biosafety guidelines for researchers working with rDNA. The Asilomar Conference was one of the first instances when scientists gathered independently to discuss and establish precautionary guidelines for research using rDNA, a technology with the potential for wide-reaching applications for medicine, biology, and reproduction.

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.