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Barbara McClintock's Transposon Experiments in Maize (1931–1951)
Barbara McClintock conducted experiments on corn (Zea mays) in the United States in the mid-twentieth century to study the structure and function of the chromosomes in the cells. McClintock researched how genes combined in corn and proposed mechanisms for how those interactions are regulated. McClintock received the Nobel Prize in Physiology or Medicine in 1983, the first woman to win the prize without sharing it. McClintock won the award for her introduction of the concept of transposons, also called jumping genes.
Format: Articles
Subject: Experiments
The Debate over DNA Replication Before the Meselson-Stahl Experiment (1953–1957)
Between 1953 and 1957, before the Meselson-Stahl experiment verified semi-conservative replication of DNA, scientists debated how DNA replicated. In 1953, James Watson and Francis Crick proposed that DNA was composed of two helical strands that wound together in a coil. Their model suggested a replication mechanism, later termed semi-conservative replication, in which parental DNA strands separated and served as templates for the replication of new daughter strands.
Format: Articles
Subject: Theories
Victor Ambros (1953-)
Victor Ambros is a professor of molecular medicine at the University of Massachusetts Medical School, and he discovered the first microRNA (miRNA) in 1993. Ambros researched the genetic control of developmental timing in the nematode worm Caenorhabditis elegans and he helped describe gene function and regulation during the worm’s development and embryogenesis. His discovery of miRNA marked the beginning of research into a form of genetic regulation found throughout diverse life forms from plants to humans. Ambros is a central figure in the miRNA and C.
Format: Articles
Subject: People
Roy Chapman Andrews (1884-1960)
Roy Chapman Andrews traveled the world studying fossils, from mammals to dinosaurs, during the first half of the twentieth century. Andrews worked and collected fossil specimens for the American Museum of Natural History (AMNH) in New York City, New York. Throughout his career, Andrews collected bones of many animal species, including a previously unknown species of a horned, herbivorous dinosaur, later named Proceratops andrewsi in his honor. Andrews published widely read narratives about his travels and field experiences, such as On the Trail of Ancient Man and Across Mongolian Plains.
Format: Articles
Subject: People
“A Linkage Between DNA Markers on the X Chromosome and Male Sexual Orientation” (1993), by Dean H. Hamer and Charles A. Thomas.
In 1993, Dean H. Hamer and colleagues in the US published results from their research that indicated that men with speicifc genes were more likely to be homosexual than were men without those genes. The study hypothesized that some X chromosomes contain a gene, Xq28, that increases the likelihood of an individual to be homosexual. Prior to those results, researchers had argued that the cause of homosexuality was environmental and that homosexuality could be altered or reversed. Hamer’s research suggested a possible genetic cause of homosexuality.
Format: Articles
Subject: Experiments
Berthold Karl Hölldobler (1936– )
Berthold Karl Hölldobler studied social insects like ants in Europe and the US during the twentieth and early twenty-first century. He focused on the social behavior of ants, the evolutionary origins of social insects, and the way ants use chemicals to communicate with each other. Hölldobler’s research reached popular audiences through his co-authored Pulitzer Prize winning book The Ants and through an award winning nature documentary called Ameisen: Die heimliche Weltmacht (Ants: Nature’s Secret Power).
Format: Articles
"Ethical Issues in Human Stem Cell Research: Executive Summary" (1999), by the US National Bioethics Advisory Commission
Ethical Issues in Human Stem Cell Research: Executive Summary was published in September 1999 by The US National Bioethics Advisory Commission in response to a national debate about whether or not the US federal government should fund embryonic stem cell research. Ethical Issues in Human Stem Cell Research recommended policy to US President William Clinton's administration, which advocated for federal spending on the use of stem research on stem cells that came from embryos left over from in vitro fertilization (IVF) fertility treatments.
Format: Articles
Horatio Robinson Storer (1830–1922)
Horatio Robinson Storer was a surgeon and anti-abortion activist in the 1800s who worked in the field of women’s reproductive health and led the Physicians’ Crusade Against Abortion in the US. Historians credit Storer as being one of the first physicians to distinguish gynecology, the study of diseases affecting women and their reproductive health, as a separate subject from obstetrics, the study of pregnancy and childbirth.
Format: Articles
Subject: People, Reproduction, Religion
Sir D'Arcy Wentworth Thompson (1860-1948)
Known by many for his wide-reaching interests and keen thinking, D'Arcy Wentworth Thompson was one of Britain's leading scientific academics in the first few decades of the twentieth century. A prodigious author, Thompson published some 300 papers, books, and articles in the biological sciences, classics, oceanography, and mathematics. He was a famous lecturer and conversationalist-a true "scholar-naturalist," as his daughter wrote in her biography of her father.
Format: Articles
Subject: People
David Edwin Wildt (1950- )
David Edwin Wildt developed and applied assisted reproductive technologies to conserve rare and endangered wildlife species in the US during the twentieth and twenty-first centuries. He advocated genome resource banks to help preserve biodiversity, and he advocated for practical ethics to guide wildlife reproductive biologists when they use technology and environmental planning. Wildt often focused on the cheetah (Acinonyx jubatus), but he researched greater than fifty vertebrate species.
Format: Articles
Subject: People
Madison Grant (1865–1937)
Madison Grant was a lawyer and wildlife conservationist who advocated for eugenics policies in the US during the late nineteenth and early twentieth centuries. In his 1916 book, The Passing of the Great Race; or, The Racial Basis of European History, Grant argued that what he called the Nordic race, which originated from northwest Europe, was biologically and culturally superior to all other people, including other Europeans.
Format: Articles
Subject: People
Chernobyl Heart (2003)
In 2003, HBO Original Programming released the documentary Chernobyl Heart. Maryann De Leo directed and produced the film, which is about the Chernobyl nuclear power plant accident and how the radiation from that accident has affected people living in the area. Side effects have included mental disabilities, physical disabilities, and genetic mutations.
Format: Articles
Subject: Outreach
Hermaphrodites and the Medical Invention of Sex (1998), by Alice Domurat Dreger
Hermaphrodites and the Medical Invention of Sex, by historian of science Alice Domurat Dreger, was published in 1998 by Harvard University Press. In the book, Dreger describes how many doctors and scientists treated human hermaphrodites from the late nineteenth century to the early twentieth century. She states that during this time period, many physicians and scientists struggled to determine the nature sex, and to support a classification of sex as male or female, many physicians and scientists resorted to viewing a person's gonads for identification of his or her sex.
Format: Articles
Subject: Publications, Theories, Disorders
Mesoderm
Mesoderm is one of the three germ layers, groups of cells that interact early during the embryonic life of animals and from which organs and tissues form. As organs form, a process called organogenesis, mesoderm interacts with endoderm and ectoderm to give rise to the digestive tract, the heart and skeletal muscles, red blood cells, and the tubules of the kidneys, as well as a type of connective tissue called mesenchyme. All animals that have only one plane of symmetry through the body, called bilateral symmetry, form three germ layers.
Format: Articles
Subject: Processes
Epidermal Growth Factor
Epidermal growth factor is a signaling molecule that stimulates the growth of epidermal tissues during development and throughout life. Stanley Cohen discovered epidermal growth factor (EGF) during studies of nerve growth factor as a side effect of other experiments. EGF stimulates tissue growth by initiating a variety of cellular mechanisms. This work led to the 1986 Nobel Prize in Physiology or Medicine awarded to Cohen and Rita Levi-Montalcini.
Format: Articles
Subject: Processes
"How do Embryos Assess Risk? Vibrational Cues in Predator-Induced Hatching of Red-Eyed Treefrogs" (2005), by Karen Warkentin
In 'How do Embryos Assess Risk? Vibrational Cues in Predator-Induced Hatching of Red-Eyed Treefrogs' (2005), Karen Warkentin reported on experiments she conducted to see how red-eyed treefrog embryos, Agalychnis callidryas, can distinguish between vibrations due to predator attacks and other environmental occurrences, such as storms. Though the ability of red-eyed treefrogs to alter their hatch timing had been documented, the specific cues that induce early hatching were not well understood.
Format: Articles
Subject: Experiments, Organisms
Essay: Homology
Homology is a central concept of comparative and evolutionary biology, referring to the presence of the same bodily parts (e.g., morphological structures) in different species. The existence of homologies is explained by common ancestry, and according to modern definitions of homology, two structures in different species are homologous if they are derived from the same structure in the common ancestor.
Format: Essays and Theses
Subject: Processes
"Comfortably, Safely, and Without Shame: Defining Menstrual Hygiene Management as a Public Health Issue" (2015), by Marni Sommer, Jennifer S. Hirsch, Constance Nathanson, and Richard G. Parker
In July 2015, Marni Sommer and colleagues published “Comfortably, Safely, and Without Shame: Defining Menstrual Hygiene Management as a Public Health Issue,” hereafter “Defining MHM,” in American Journal of Public Health. The authors discuss that growing interest in the gender gap in education raised awareness about girls’ obstacles to managing menstruation, especially in low-income countries. Increased focus on MHM pushed menstruation to be redefined as a public issue rather than a private one.
Format: Articles
Subject: Publications
The Development of Silicone Breast Implants for Use in Breast Augmentation Surgeries in the United States
In the 1960s, two plastic surgeons from the United States, Thomas Dillon Cronin and Frank Judson Gerow, collaborated with the Dow Corning Corporation, which specialized in silicone products, to create the first silicone breast implant. Surgeons used the implant, named the Cronin-Gerow implant, to improve the look of a woman’s breasts, by correcting for asymmetry, augmenting the size, or creating a more uplifted profile.
Format: Articles
Subject: Technologies, Processes
Magnetic Resonance Microscopy (MRM)
Magnetic Resonance Microscopy (MRM) is an imaging method that allows the visualization of internal body structures. Using powerful magnets to send energy into cells, MRM picks up signals from inside a specimen and translates them into detailed computer images. MRM is a useful tool for scientists because of its ability to generate digital slices of scanned specimens that can be constructed into virtual 3D images without destroying the specimens. MRM has become an increasingly prevalent imaging technique in embryological studies.
Format: Articles
Subject: Technologies
Ethics and Induced Pluripotent Stem Cells
The recent development of induced pluripotent stem cells (iPSCs) and related technologies has caught the attention of scientists, activists, politicians, and ethicists alike. IPSCs gained immediate international attention for their apparent similarity to embryonic stem cells after their successful creation in 2006 by Shinya Yamanaka and in 2007 by James Thompson and others.
Format: Articles
Subject: Technologies, Ethics
Alec John Jeffreys (1950–)
Alec John Jeffreys created a process called DNA fingerprinting in the UK during the twentieth century. For DNA fingerprinting, technicians identify a person as the source of a biological sample by comparing the genetic information contained in the person's DNA to the DNA contained in the sample. Jeffreys developed the technique in the 1980s while at the University of Leicester in Leicester, UK. Jeffreys's technique had immediate applications. In forensic science, DNA fingerprinting enabled police to identify suspects of crimes based on their genetic identities.
Format: Articles
Subject: People
The Southern Gastric-Brooding Frog
The Southern Gastric-Brooding Frog (Rheobatrachus silus) was an aquatic frog that lived in south-east Australia. In 2002, the International Union for Conservation of Nature Red List declared the frog extinct, although no wild specimens had been reported since 1981. As the common name alludes to, the R.
Format: Articles
Subject: Organisms
Josef Warkany (1902–1992)
Josef Warkany studied the environmental causes of birth defects in the United States in the twentieth century. Warkany was one of the first researchers to show that factors in the environment could cause birth defects, and he helped to develop guidelines for the field of teratology, the study of birth defects. Prior to Warkany’s work, scientists struggled to explain if or how environmental agents could cause birth defects. Warkany demonstrated that a deficiency or excess of vitamin A in maternal nutrition could cause birth defects.
Format: Articles
Subject: People
Ontogeny and Phylogeny (1977), by Stephen Jay Gould
Ontogeny and Phylogeny is a book published in 1977, in which the author Stephen J. Gould, who worked in the US, tells a history of the theory of recapitulation. A theory of recapitulation aims to explain the relationship between the embryonic development of an organism (ontogeny) and the evolution of that organism's species (phylogeny). Although there are several variations of recapitulationist theories, most claim that during embryonic development an organism repeats the adult stages of organisms from those species in it's evolutionary history.
Format: Articles
Subject: Publications