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Intraspecies Chimeras Produced in Laboratory Settings (1960-1975)
When cells-but not DNA-from two or more genetically distinct individuals combine to form a new individual, the result is called a chimera. Though chimeras occasionally occur in nature, scientists have produced chimeras in a laboratory setting since the 1960s. During the creation of a chimera, the DNA molecules do not exchange genetic material (recombine), unlike in sexual reproduction or in hybrid organisms, which result from genetic material exchanged between two different species. A chimera instead contains discrete cell populations with two unique sets of parental genes.
Format: Articles
Victor Jollos (1887-1941)
Victor Jollos studied fruit flies and microorganisms in Europe and the US, and he introduced the concept of Dauermodifikationen in the early 1900s. The concept of Dauermodifikationen refers to environmentally-induced traits that are heritable for only a limited number of generations. Some scientists interpreted the results of Jollos's work on Paramecium and Drosophila as
Format: Articles
Subject: People
Hematopoietic Stem Cell Transplantation
The purpose of regenerative medicine, especially tissue engineering, is to replace damaged tissue with new tissue that will allow the body to resume normal function. The uniqueness of tissue engineering is that it can restore normal structure in addition to repairing tissue function, and is often accomplished using stem cells. The first type of tissue engineering using stem cells was hematopoietic stem cell transplantation (HSCT), a surgical procedure in which hematopoietic stem cells (HSCs) are infused into a host to treat a variety of blood diseases, cancers, and immunodeficiencies.
Format: Articles
Subject: Technologies
Golden Rice
Golden Rice was engineered from normal rice by Ingo Potrykus and Peter Beyer in the 1990s to help improve human health. Golden Rice has an engineered multi-gene biochemical pathway in its genome. This pathway produces beta-carotene, a molecule that becomes vitamin A when metabolized by humans. Ingo Potrykus worked at the Swiss Federal Institute of Technology in Zurich, Switzerland, and Peter Beyer worked at University of Freiburg, in Freiburg, Germany. The US Rockefeller Foundation supported their collaboration.
Format: Articles
Wolbachia
Bacteria of the genus Wolbachia are
bacteria that live within the cells of their hosts. They infect a
wide range of arthropods (insects, arachnids, and crustaceans) and
some nematodes (parasitic roundworms). Scientists estimate that
Wolbachia exist in between seventeen percent and seventy-six percent of
arthropods and nematodes. The frequency of the bacteria makes them
one of the most widespread parasites. In general, they are divided
into five groups, from A to E, depending of the species of their
Format: Articles
Subject: Organisms
“Child Development in the Context of Disaster, War, and Terrorism: Pathways of Risk and Resilience” (2012), by Ann S. Masten and Angela J. Narayan
In 2012 Ann S. Masten and Angela J. Narayan published the article “Child Development in the Context of Disaster, War, and Terrorism: Pathways of Risk and Resilience” in Annual Reviews in Psychology. The authors conducted their study at the Institute of Child Development at the University of Minnesota in Minneapolis, Minnesota. In the article, Masten and Narayan review a number of articles to examine and compile the research made since the twenty-first century on the psychological impact of mass trauma, such as war, terrorism, and disasters, on children.
Format: Articles
Subject: Publications
40 Weeks (2014)
In 2014, Big Belli, a media and social networking brand, released a documentary called 40 Weeks online. The documentary, directed by Christopher Henze, followed multiple women during their pregnancies. The film predominantly features three women, though it includes the stories of many. Throughout the film, women detail their accounts of the physical and emotional changes that occur during pregnancy.
Format: Articles
Subject: Publications
Stafford Leak Warren (1896–1981)
Stafford Leak Warren studied nuclear medicine in the United States during the twentieth century. He used radiation to make images of the body for diagnosis or treatment and developed the mammogram, a breast imaging technique that uses low-energy X-rays to produce an image of breasts. Mammograms allow doctors to diagnose breast cancer in its early and most treatable stages.
Format: Articles
Subject: People
Pennsylvania Association for Retarded Citizens (PARC) v. Commonwealth of Pennsylvania (1972)
In 1972, the United States District Court for the Eastern District of Pennsylvania decided the case of Pennsylvania Association for Retarded Citizens (PARC) v. Commonwealth of Pennsylvania, hereafter PARC v. Pennsylvania. The court ruled that the state could not deny an individual's right to equal access to education based on an intellectual or developmental disability status. PARC brought the case against the state of Pennsylvania on behalf of fourteen families with intellectually disabled children who were unable to access to public schools based on their child’s disability.
Format: Articles
In re Agent Orange Product Liability Litigation (1979-1984)
In the legal case In re Agent Orange Product Liability Litigation of the early 1980s, US military veterans of the Vietnam War sued the US chemical companies that had produced the herbicide Agent Orange, and those companies settled with US veterans out of court. Agent Orange contains dioxin, a chemical later shown to disrupt the hormone system of the body and to cause cancer. As veterans returned to the US from Vietnam, scientists further confirmed that exposure to Agent Orange caused a variety of cancers in veterans and developmental problems in the veterans' children.
Format: Articles
Bernard Sachs (1858-1944)
Bernard Sachs studied nervous system disorders in children in the
United States during the nineteenth and twentieth centuries. In the
late 1880s, Sachs described the fatal genetic neurological disorder
called amaurotic family idiocy, later renamed Tay-Sachs disease. The
disorder degrades motor skills as well as mental abilities in
affected individuals. The expected lifespan of a child with
Tay-Sachs is three to five years. In addition to working on
Tay-Sachs disease, Sachs described other childhood neurological and
Format: Articles
Subject: People
Benjamin Harrison Willier (1890-1972)
Benjamin Harrison Willier is considered one of the most versatile embryologists to have ever practiced in the US. His research spanned most of the twentieth century, a time when the field of embryology evolved from being a purely descriptive pursuit to one of experimental research, to that of incorporating molecular biology into the research lab. Willier was born on 2 November 1890 near Weston, Ohio to Mary Alice Ricard. He spent his childhood doing farming chores and running the farm while his father, David Willier worked as a banker.
Format: Articles
Subject: People
Congenital Vertebral Defects
The spinal column is the central structure in the vertebrate body from which stability, movement, and posture all derive. The vertebrae of the spine are organized into four regions (listed in order from cranial to caudal): cervical, thoracic, lumbar, and pelvic. These regions are classified by their differences in curvature. The human spine usually consists of thirty-three vertebrae, seven of which are cervical (C1-C7), twelve are thoracic (T1-T12), five are lumbar (L1-L5), and nine are pelvic (five fused as the sacrum and four fused as the coccyx).
Format: Articles
Subject: Disorders, Reproduction
"The Limited In Vitro Lifetime of Human Diploid Cell Strains" (1964), by Leonard Hayflick
Leonard Hayflick in the US during the early 1960s showed that normal populations of embryonic cells divide a finite number of times. He published his results as 'The Limited In Vitro Lifetime of Human Diploid Cell Strains' in 1964. Hayflick performed the experiment with WI-38 fetal lung cells, named after the Wistar Institute, in Philadelphia, Pennsylvania, where Hayflick worked. Frank MacFarlane Burnet, later called the limit in capacity for cellular division the Hayflick Limit in 1974.
Format: Articles
Subject: Experiments
August Friedrich Leopold Weismann (1834-1914)
August Friedrich Leopold Weismann studied how the traits of organisms developed and evolved in a variety of organisms, mostly insects and aquatic animals, in Germany in the late nineteenth and early twentieth centuries. Weismann proposed the theory of the continuity of germ-plasm, a theory of heredity. Weismann postulated that germ-plasm was the hereditary material in cells, and parents transmitted to their offspring only the germ-plasm present in germ-cells (sperm and egg cells) rather than somatic or body cells.
Format: Articles
Subject: People
"A molecular wound response program associated with regeneration initiation in planarians" (2012), by Danielle Wenemoser et al.
In 2012, a team of scientists across the US conducted an experiment to find the mechanism that allowed a group of flatworms, planarians, to regenerate any body part. The group included Danielle Wenemoser, Sylvain Lapan, Alex Wilkinson, George Bell, and Peter Reddien. They aimed to identify genes that are expressed by planarians in response to wounds that initiated a regenerative mechanism. The researchers determined several genes as important for tissue regeneration.
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
John von Neumann's Cellular Automata
Cellular automata (CA) are mathematical models used to simulate complex systems or processes. In several fields, including biology, physics, and chemistry, CA are employed to analyze phenomena such as the growth of plants, DNA evolution, and embryogenesis. In the 1940s John von Neumann formalized the idea of cellular automata in order to create a theoretical model for a self-reproducing machine. Von Neumann's work was motivated by his attempt to understand biological evolution and self-reproduction.
Format: Articles
Subject: Theories
"Testing the Kin Selection Theory: Who Controls the Investments?" from The Ants (1990), by Bert Hölldobler and Edward O. Wilson
In “Testing the Kin Selection Theory: Who Controls the Investments?” Bert Hölldobler and Edward Osborne Wilson discussed the predictive power of kin selection theory, a theory about the evolution of social behaviors. As part of Hölldobler's and Wilson's 1990 book titled The Ants, Hölldobler and Wilson compared predictions about the reproductive practices of ants to data about the reproductive practices of ants. They showed that the data generally supported the expected behaviors proposed by kin selection theory.
Format: Articles
Subject: Publications, Theories
George Frederic Still (1868–1941)
George Frederic Still studied pediatrics and childhood conditions in England during the early twentieth century. In Still’s time, pediatrics, or the branch of medicine that focuses on treating and caring for children, remained largely unexplored according to biographer Joseph deBettencourt. Still helped advance pediatrics as a field by classifying and writing about diseases and conditions that arose in children. In 1897, he discovered a unique type of arthritis in children, now referred to as Still’s disease.
Format: Articles
Subject: People
Peter Mazur (1928–2015)
Peter Mazur was a researcher in the US who developed new ways of preserving biological material by freezing it, a process called cryopreservation. If done correctly, cryopreservation enables scientists to store or study biological material for an extended period of time. If done incorrectly, cryopreservation can easily harm or destroy biological material. Mazur worked to find the best ways to cryopreserve different cells, embryos, and organs in order to minimize the damage caused by freezing.
Format: Articles
Subject: People
Alec Jeffreys’s Experiments to Identify Individuals by Their Beta-globin Genes (1977-1979)
In a series of experiments in the late 1970s, Alec J. Jeffreys in the UK and Richard A. Flavell in the Netherlands developed a technique to detect variations in the DNA of different individuals. They compared fragments of DNA from individuals’ beta-globin genes, which produce a protein in hemoglobin. Previously, to identify biological material, scientists focused on proteins rather than on genes. But evidence about proteins enabled scientists only to exclude, but not to identify, individuals as the sources of the biological samples.
Format: Articles
Subject: Experiments
Oliver Allison Ryder III (1946– )
Oliver Allison Ryder studied chromosomal evolution and endangered species in efforts for wildlife conservation and preservation at the San Diego Zoo in San Diego, California. Throughout his career, Ryder studied breeding patterns of endangered species. He collected and preserved cells, tissues, and DNA from endangered and extinct species to store in the San Diego Frozen Zoo, a center for genetic research and development in San Diego, California.
Format: Articles
Subject: People
"Interspecific Chimeras in Mammals: Successful Production of Live Chimeras Between Mus musculus and Mus caroli" (1980), by Janet Rossant and William I. Frels
In 1980 Janet Rossant and William I. Frels published their paper, "Interspecific Chimeras in Mammals: Successful Production of Live Chimeras Between Mus musculus and Mus caroli," in Science. Their experiment involved the first successful creation of interspecific mammalian chimeras. Mammalian chimeras are valuable for studying early embryonic development. However, in earlier studies, clonal analysis was restricted by the lack of a cell marker, present at all times, that makes a distinction between the two parental cell types in situ.
Format: Articles
Subject: Experiments
Hermann Joseph Muller's Study of X-rays as a Mutagen, (1926-1927)
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".
Format: Articles
Subject: Experiments