In 1962 researcher John Bertrand Gurdon at the University of Oxford in Oxford, England, conducted a series of experiments on the developmental capacity of nuclei taken from intestinal epithelium cells of feeding tadpoles. In the experiments, Gurdon conducted nuclear transplantation, or cloning, of differentiated cells, or cells that have already specialized to become one cell type or another, in tadpoles. Gurdon's experiment showed that differentiated adult cells could be induced to an undifferentiated state, where they could once again become multiple cell types. Gurdon's experiment disproved the theory that differentiated cells could not be undifferentiated or dedifferentiated into a new type of differentiated cell. Gurdon's experiment demonstrated nuclear transplantation, also called cloning, using differentiated cells.

Hermann Joseph Muller conducted three experiments in 1926 and 1927 that demonstrated that exposure to x-rays, a form of high-energy radiation, can cause genetic mutations, changes to an organism's genome, particularly in egg and sperm cells. In his experiments, Muller exposed fruit flies (Drosophila) to x-rays, mated the flies, and observed the number of mutations in the offspring. In 1927, Muller described the results of his experiments in "Artificial Transmutation of the Gene" and "The Problem of Genic Modification". His discovery indicated the causes of mutation and for that research he later received the Nobel Prize in Physiology or Medicine in 1946. Muller's experiments with x-rays established that x-rays mutated genes and that egg and sperm cells are especially susceptible to such genetic mutations.

During 1964, David Hubel and Torsten Wiesel studied the short and long term effects of depriving kittens of vision in one eye. In their experiments, Wiesel and Hubel used kittens as models for human children. Hubel and Wiesel researched whether the impairment of vision in one eye could be repaired or not and whether such impairments would impact vision later on in life. The researchers sewed one eye of a kitten shut for varying periods of time. They found that when vision impairments occurred to the kittens right after birth, their vision was significantly affected later on in life, as the cells that were responsible for processing visual information redistributed to favor the unimpaired eye. Hubel and Wiesel worked together for over twenty years and received the 1981 Nobel Prize for Physiology or Medicine for their research on the critical period for mammalian visual system development. Hubel and Wiesel’s experiments with kittens showed that there is a critical period during which the visual system develops in mammals, and it also showed that any impairment of that system during that time will affect the lifelong vision of a mammal.

The book Infant Mortality: Results of a Field Study in Johnstown, PA., Based on Births in One Calendar Year (1915), written by Emma Duke, detailed one of the first infant mortality field studies conducted by the US Children's Bureau. In the study, Duke and her colleagues collected information about over one thousand infants in the city of Johnstown, Pennsylvania. They used that information, along with interviews conducted with the families of the infants, to identify factors that affected infant mortality rates in the community. Duke and her team found strong correlations between elevated infant mortality rates and conditions experienced by Johnstown residents of lower socioeconomic status. The design and implementation of the study described in Infant Mortality: Johnstown, PA provided a model for future Children's Bureau research that resulted in seven additional infant mortality studies in other US cities. Infant Mortality: Results of a Field Study in Johnstown, PA., Based on Births in One Calendar Year quantitatively demonstrated the link between poverty and infant mortality.

In 1952, researchers Christopher Polge and Lionel Edward Aston Rowson, who worked at the Animal Research Center in Cambridge, England, detailed several experiments on protocols for freezing bull semen for use in the artificial insemination of cows. Freezing sperm extends the life of a viable sperm sample and allows it to be used at later times, such as in artificial insemination. The researchers examined the effects of freezing conditions on bull sperm and how well they produce fertilized embryos once thawed. Polge and Rowson concluded that bull sperm can retain its fertility throughout the freezing process and that frozen bull sperm can yield pregnancy rates of up to seventy-nine percent. Polge and Rowson provided the first conclusive evidence that frozen mammalian sperm, once thawed, can produce viable pregnancies.

In 2015, Junjiu Huang and his colleagues reported their attempt to enable CRISPR/cas 9-mediated gene editing in nonviable human zygotes for the first time at Sun Yat-Sen University in Guangzhou, China. Their article, CRISPR /Cas9-mediated Gene Editing in Human Tripronuclear Zygotes, was published in Protein and Cell. Nonviable zygotes are sperm-fertilized eggs that cannot develop into a fetus. Researchers previously developed the CRISPR/cas 9 gene editing tool, which is a system that originated from bacteria as a defense mechanism against viruses. In their article, Huang and his team demonstrate that CRISPR/cas-9 gene editing can be used to correct a mutation in zygotes, or sperm-fertilized egg cells. However, they report that using CRISPR/cas 9 to edit those nonviable human zygotes led to off-target changes and, therefore, to unintended mutations in the human genome. Before Huang and his colleagues' experiment, CRISPR/cas 9 had never been used on human zygotes. In their article, Huang and his colleagues demonstrated the need to improve CRISPR/cas 9 gene editing accuracy before using it for gene therapy to treat and correct genetic diseases in humans.

Between 1935 and 1937, Leonard Colebrook showed that sulfonamides, a class of antibacterial drugs, worked as an effective treatment for puerperal fever. Puerperal fever is a bacterial infection that can occur in the uterus of women after giving birth. At the time of Colebrook’s study, puerperal fever remained a common disease due to both the lack of hygienic practices in hospitals and a treatment for the disease. After successfully using Prontosil, a sulfanilamide, to cure a patient who was going to die from puerperal fever, Colebrook began experiments with the drug. He successfully treated patients with puerperal fever with sulfonamides, specifically Prontosil and sulfanilamide. Colebrook conducted the experiment from 1935 to 1936 primarily at the Queen Charlotte’s Hospital in London, England. After Colebrook’s success using antibacterial drugs in treating puerperal fever, use of antibacterial drugs became widespread in developed countries and, by the 1950s, it had made maternal deaths rare in those countries.

In 2007, Dennis Lo and his colleagues used digital polymerase chain reaction or PCR to detect trisomy 21 in maternal blood, validating the method as a means to detect fetal chromosomal aneuploidies, or an abnormal number of chromosomes in a cell. The team conducted their research at the Chinese University of Hong Kong in Hong Kong, Hong Kong, and at the Boston University in Boston, Massachusetts. Because small amounts of fetal DNA appear in maternal blood during pregnancy, Lo and his team hypothesized that they could detect fetal chromosomal aneuploidy trisomy 21, or Down’s syndrome, in a sample of maternal blood. The group diagnosed Down’s syndrome in unborn fetuses by first taking a maternal blood sample, then amplifying the small amounts of fetal DNA in the maternal blood using digital PCR, and applying two genetic methods to that sample. Lo and his colleagues’ experiment demonstrated the accuracy of a novel, noninvasive method for fetal chromosomal aneuploidy testing that can enable people to make informed decisions about their pregnancies.

In 2007, Philippe Horvath and his colleagues explained how bacteria protect themselves against viruses at Danisco, a Danish food company, in Dangé-Saint-Romain, France. Horvath and his team worked to improve the lifespan of bacteria cultures for manufacturing yogurt and ice cream. Specifically, they focused on bacteria’s resistance to bacteriophages, or viruses that infect bacteria. Horvath and his colleagues found that the bacteria used to culture yogurt, Streptococcus thermophilus, has an adaptive immune system that can target specific viruses that have previously infected the bacteria. The immune system is called the CRISPR/cas system, or the clustered regularly interspaced short palindromic repeats/CRISPR associated protein system. Horvath and his colleagues explained how bacteria use CRISPR/cas as an immune system to target viruses and protect themselves from infection. The discovery informed the development of CRISPR/cas as a gene editing tool to modify bacterial, animal, and human genomes.

Shoukhrat Mitalipov, Masahito Tachibana, and their team of researchers replaced the mitochondrial genes of primate embryonic stem cells via spindle transfer. Spindle replacement, also called spindle transfer, is the process of removing the genetic material found in the nucleus of one egg cell, or oocyte, and placing it in another egg that had its nucleus removed. Mitochondria are organelles found in all cells and contain some of the cell’s genetic material. Mutations in the mitochondrial DNA can lead to neurodegenerative and muscle diseases. Mitalipov and Tachibana used spindle replacement to produce healthy offspring from an egg with mutated mitochondria in rhesus macaques (Macaca mulatta). The experiment showed that spindle transfer eliminated the chance of transmission of mitochondrial diseases from the affected primates to their offspring, offering the potential to eliminate mitochondrial diseases in humans.