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Molecular Epigenetics and Development: Histone Conformations, DNA Methylation and Genomic Imprinting
Introduced by Conrad Hal Waddington in 1942, the concept of epigenetics gave scientists a new paradigm of thought concerning embryonic development, and since then has been widely applied, for instance to inheritable diseases, molecular technologies, and indeed the human genome as a whole. A genome contains an embedded intricate coding template that provides a means of genetic expression from the initial steps of embryonic development until the death of the organism. Within the genome there are two prominent components: coding (exons) and non-coding (introns) sequences.
Conrad Hal Waddington (1905-1975)
Conrad Hal Waddington was an embryologist and theoretical biologist. His early experimental work investigated aspects of embryonic induction and the properties of the organizer first identified by Hans Spemann and Hilde Mangold, while his later studies focused on genetic assimilation. Waddington is probably best known for developing the concept of the epigenetic landscape, and he also held significant interest in many different areas ranging from the visual arts and poetry to philosophy.
Facial Abnormalities of Fetal Alcohol Syndrome (FAS)
Prenatal exposure to alcohol (ethanol) results in a continuum of physical, neurological, behavioral, and learning defects collectively grouped under the heading Fetal Alcohol Spectrum Disorder (FASD). Fetal Alcohol Syndrome (FAS) was first defined in 1973 as a condition characterized by pre- and postnatal growth deficiencies, facial abnormalities, and defects of the central nervous system. The pattern of facial defects that occur as a result of ethanol exposure during development primarily affects the midline of the face, altering morphology of the eyes, nose, and lips.
Subject: Disorders, Reproduction
Karl Ernst von Baer's Laws of Embryology
In 1828, while working at the University of Konigsberg in Konigsberg, Germany Karl Ernst von Baer proposed four laws of animal development, which came to be called von Baer's laws of embryology. With these laws, von Baer described the development (ontogeny) of animal embryos while also critiquing popular theories of animal development at the time.
Christian Heinrich Pander (1794-1865)
Christian Heinrich Pander, often remembered as the father of embryology, also explored the fields of osteology, zoology, geology, and anatomy. He was born in Riga, Latvia, on 24 July 1794. Pander, with an eclectic history of research, is best remembered for his discovery and explanation of the structure of the chick blastoderm, a term he coined. In doing so, Pander was able to achieve the goal set forth by his teacher, Ignaz Döllinger, to reinvigorate the study of the chick embryo as a means of further exploring the science of embryology as a whole.
The Case of Lydia Fairchild and Her Chimerism (2002)
In 2002, after applying for government assistance in the state of Washington, Lydia Fairchild was told that her two children were not a genetic match with her and that therefore, biologically, she could not be their mother. Researchers later determined that the genetic mismatch was due to chimerism, a condition in which two genetically distinct cell lines are present in one body. The state accused Fairchild of fraud and filed a lawsuit against her.
Hamburger-Hamilton Staging Series (1951)
In 1951 Viktor Hamburger and Howard Hamilton created an embryonic staging series from a combination of photographs and drawings from other researchers. The Hamburger-Hamilton stages are a sequence of images depicting 46 chronological stages in chick development. The images begin with a fertilized egg and end with a fully developed chick. The Hamburger-Hamilton staging series was produced in order to replace a previous chick staging series created in 1900. The earlier attempt lacked specific details and staged the chick embryo by using only morphological characteristics.
Leo Loeb (1869-1959)
Leo Loeb developed an experimental approach to studying cancer and pioneered techniques for tissue culture and in vitro tissue transplantation which impacted early-to-mid twentieth century experimental embryology. Loeb received his medical degree from the University of Zurich in 1897. As part of his doctorate, he completed a thesis on the outcomes of tissue transplantation in guinea pigs. Loeb's thesis inspired a life-long interest in tissue transplantation.
John George Children (1777–1852)
John George Children described several species of insects and animals while working at the British Museum in London, England, in the eighteenth and nineteenth centuries. Children also conducted research on chemical batteries called voltaic cells and briefly studied and manufactured gunpowder. One of the species he described, the Children’s python, or Antaresia children, was used in the twenty-first century as the subject of experiments that involved the biological cost of reproduction in snakes.
Arizona State University Embryo Project Photograph Collections
In the 1970s Stanford University Embryologist Harold Heath sent a box of photographs to Frederick B. Churchill, who was a Professor in the History and Philosophy of Science Department at Indiana University. Heath was born in Indiana, he knew that Churchill was the leading historian of embryology, and he wanted his photographs to be used and therefore wanted them to be housed somewhere with an interest in the history of biology. Heath made it clear that he was donating the photographs for use by scholars and the public.
Ross Granville Harrison (1870-1959)
A pioneer in experimental embryology, Ross Granville Harrison made numerous discoveries that advanced biology. One of the most significant was his adaptation of the hanging drop method from bacteriology to carry out the first tissue culture. This method allowed for further studies in embryology as well as experimental improvements in oncology, virology, genetics, and a number of other fields.
Min Chueh Chang (1908-1991)
As one of the researchers involved in the development of the oral contraceptive pill, Min Chueh Chang helped to revolutionize the birth control movement. Although best known for his involvement with "the pill," Chang also made a number of discoveries throughout his scientific career involving a range of topics within the field of reproductive biology. He published nearly 350 articles in scientific journals.
Subject: People, Reproduction
Katharine McCormick (1876-1967)
Katharine Dexter McCormick, who contributed the majority of funding for the development of the oral contraceptive pill, was born to Josephine and Wirt Dexter on 27 August 1875 in Dexter, Michigan. After growing up in Chicago, Illinois, she attended the Massachusetts Institute of Technology (MIT), where she graduated in 1904 with a BS in biology. That same year, she married Stanley McCormick, the son of Cyrus McCormick, inventor and manufacturer of the mechanized reaper.
Subject: People, Ethics, Reproduction
Rosalyn Sussman Yalow (1921-2011)
Rosalyn Sussman Yalow co-developed the radioimmunoassay (RIA), a method used to measure minute biological compounds that cause immune systems to produce antibodies. Yalow and research partner Solomon A. Berson developed the RIA in the early 1950s at the Bronx Veterans Administration (VA) Hospital, in New York City, New York. Yalow and Berson's methods expanded scientific research, particularly in the medical field, and contributed to medical diagnostics. For this achievement, Yalow received the Nobel Prize in Physiology or Medicine in 1977.
Tomorrow's Children (1934)
Tomorrow's Children is a film that tells the story of Alice Mason, a young woman whom the US government forcibly sterilizes because she comes from a family with a history of alcoholism, mental illnesses, and physical disabilities, traits that they considered biologically determined and inferior. The film, released in 1934, was directed by Crane Wilbur, produced by Bryan Foy, written by Wilbur and Wallace Thurman, and released by Foy Productions Ltd.
“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.
Libbie Henrietta Hyman (1888-1969)
Libbie Henrietta Hyman was born into a recently immigrated Jewish family on 6 December 1888 in Des Moines, Iowa. One of many siblings and daughter to parents Sabina Neumann and Joseph Hyman, who did not particularly support her interests in science, Hyman excelled in school and indulged her interests in biology in her free time. From a young age, Hyman collected and cataloged flora around her home. Despite being valedictorian of her high school class, Hyman's first job was labeling cereal boxes in a local factory.
Roman v. Roman (2006)
In the case Randy M. Roman v. Augusta N. Roman (2006), the Court of Appeals of Texas followed courts in other states and upheld the validity and enforceability of in vitro fertilization (IVF) consent agreements. The Romans, a divorced couple, each sought different outcomes for their cryopreserved preembryos created during their marriage. Randy Roman sought to have them destroyed, and Augusta Roman sought to implant them in an attempt to have biological children.
Francis Galton (1822-1911)
Sir Francis Galton was a British science writer and amateur researcher of the late nineteenth century. He contributed greatly to the fields of statistics, experimental psychology and biometry. In the history of biology, Galton is widely regarded as the originator of the early twentieth century eugenics movement. Galton published influential writings on nature versus nurture in human personality traits, developed a family study method to identify possible inherited traits, and devised laws of genetic inheritance prior to the rediscovery of Gregor Mendel's work.
Subject: People, Reproduction
Franz Josef Kallmann (1897–1965)
Franz Josef Kallmann studied the biological and genetic factors of psychological disorders in Germany and the United States in the twentieth century. His studies at the New York State Psychiatric Institute in New York City, New York, focused on the genetic factors that cause psychiatric disorders. Kallmann was one of the first to use twins to study how a mental disorder is passed on by comparing the occurrence of epilepsy and schizophrenia in both fraternal and identical twins.
Beatrice Mintz (1922–2022)
Beatrice Mintz is a brilliant researcher who has developed techniques essential for many aspects of research on mouse development. She produced the first successful mouse chimeras and meticulously characterized their traits. She has worked with various cancers and produced viable mice from the cells of a teratoma. Mintz participated in the development of transgenic mice by the incorporation of foreign DNA into a mouse genome.
James G. Wilson's Six Principles of Teratology
James Graves Wilson's six principles of teratology, published in 1959, guide research on teratogenic agents and their effects on developing organisms. Wilson's six principles were inspired by Gabriel Madeleine Camille Dareste's five principles of experimental teratology published in 1877. Teratology is the study of birth defects, and a teratogen is something that either induces or amplifies abnormal embryonic or fetal development and causes birth defects.
Subject: Processes, Reproduction
Johannes Holtfreter (1901-1992)
Johannes Holtfreter made important discoveries about the properties of the organizer discovered by Hans Spemann. Although he spent much time away from the lab over many years, he was a productive researcher. His colleagues noted that the time he spent away helped revitalize his ideas. He is credited with the development of a balanced salt medium to allow embryos to develop; the discovery that dead organizer tissue retains inductive abilities; and the development of specification, competence, and distribution of fate maps in the developing frog embryo.
Somites: Formation and Role in Developing the Body Plan
Somites are blocks of mesoderm that are located on either side of the neural tube in the developing vertebrate embryo. Somites are precursor populations of cells that give rise to important structures associated with the vertebrate body plan and will eventually differentiate into dermis, skeletal muscle, cartilage, tendons, and vertebrae. Somites also determine the migratory paths of neural crest cells and of the axons of spinal nerves.
"Embryonic Stem Cell Lines Derived from Human Blastocytes" (1998), by James Thomson
After becoming chief pathologist at the University of Wisconsin-Madison Wisconsin Regional Primate Center in 1995, James A. Thomson began his pioneering work in deriving embryonic stem cells from isolated embryos. That same year, Thomson published his first paper, "Isolation of a Primate Embryonic Stem Cell Line," in Proceedings of the National Academy of Sciences of the United States of America, detailing the first derivation of primate embryonic stem cells. In the following years, Thomson and his team of scientists - Joseph Itskovitz-Eldor, Sander S. Shapiro, Michelle A.
Subject: Experiments, Publications