Embryo Project Encyclopedia Articles

On 6 May 1952, at King’s College London in London, England, Rosalind Franklin photographed her fifty-first X-ray diffraction pattern of deoxyribosenucleic acid, or DNA. Photograph 51, or Photo 51, revealed information about DNA’s three-dimensional structure by displaying the way a beam of X-rays scattered off a pure fiber of DNA. Franklin took Photo 51 after scientists confirmed that DNA contained genes. Maurice Wilkins, Franklin’s colleague showed James and Francis Crick Photo 51 without Franklin’s knowledge. Watson and Crick used that image to develop their structural model of DNA. In 1962, after Franklin’s death, Watson, Crick, and Wilkins shared the Nobel Prize in Physiology or Medicine for their findings about DNA. Franklin’s Photo 51 helped scientists learn more about the three-dimensional structure of DNA and enabled scientists to understand DNA’s role in heredity.

In April 1953, Rosalind Franklin and Raymond Gosling, published “Molecular Configuration in Sodium Thymonucleate,” in the scientific journal Nature. The article contained Franklin and Gosling’s analysis of their X-ray diffraction pattern of thymonucleate or deoxyribonucleic acid, known as DNA. In the early 1950s, scientists confirmed that genes, the heritable factors that control how organisms develop, contained DNA. However, at the time scientists had not determined how DNA functioned or its three-dimensional structure. In their 1953 paper, Franklin and Gosling interpret X-ray diffraction patterns of DNA fibers that they collected, which show the scattering of X-rays from the fibers. The patterns provided information about the three-dimensional structure of the molecule. “Molecular Configuration in Sodium Thymonucleate” shows the progress Franklin and Gosling made toward understanding the three-dimensional structure of DNA.

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. Andrews led expeditions for the Central Asiatic Expeditions in the Gobi Desert, which recovered many previously unknown fossil specimens. His Central Asiatic team discovered the first scientifically recognized dinosaur eggs, which provided scientists with information about the eggs that dinosaurs produced.

Oviraptor philoceratops was a small bird-like dinosaur that lived about seventy-five million years ago, during the late Cretaceous period. In 1923, George Olsen of the American Museum of Natural History (AMNH) in New York City, New York, discovered the first Oviraptor fossilized skeleton on top of a dinosaur egg nest in the Gobi Desert, Mongolia. Because of the close proximity of dinosaur and nest, when Henry Fairfield Osborn president of the AMNH published on the discovery, he assumed that the Oviraptor had died attempting to steal the eggs. However, since the initial discovery, more Oviraptor adults, eggs, and a well-preserved embryo fossil have confirmed that Oviraptors were parents who sat on their nests, a behavior called brooding common among birds. The fossils of Oviraptor philoceratops, from eggs and embryos to adults, provide evidence about dinosaur growth, development, and reproductive behaviors.

In 1994, Edward M. Connor and colleagues published “Reduction of Maternal-Infant Transmission of Human Immunodeficiency Virus Type 1 with Zidovudine Treatment.” Their study summarized how to reduce the transfer of human immunodeficiency virus, or HIV, from pregnant women to their fetuses with Zidovudine, otherwise known as AZT. HIV is a virus that weakens the immune system by destroying white blood cells, a part of the body’s immune system. Fifteen to forty percent of infants born to HIV-positive mothers become infected during fetal development, labor and delivery, or breast-feeding. From April 1991 to December 1993, Connor and his colleagues researched HIV-positive pregnant women who took AZT, a drug that treats but does not cure an HIV infection. In their article, Conner and colleagues showed that AZT decreased the maternal-infant transmission of HIV and helped decrease infant mortality due to the viral infection.

In January 2014, Mary Gatter and colleagues published “Relationship between Ultrasound Viewing and Proceeding to Abortion” in Obstetrics and Gynecology hereafter “Ultrasound Viewing.” As of 2021, ten states require women to undergo an ultrasound before they may consent to having an abortion. Self-described pro-life organizations assert that viewing an image of the fetus will dissuade women from having an abortion. The authors reviewed women’s medical records from over fifteen thousand visits to one abortion provider in 2011.The authors determined viewing an ultrasound image did not change the minds of women who were already highly certain that abortion was the right decision, challenging the idea that mandatory ultrasound viewing has any effect on women’s decision to have an abortion.

In 2015, biologist Helena D. Zomer and colleagues published the review article “Mesenchymal and Induced Pluripotent Stem Cells: General Insights and Clinical Perspectives” or “Mesenchymal and Induced Pluripotent Stem Cells” in Stem Cells and Cloning: Advances and Applications. The authors reviewed the biology of three types of pluripotent stem cells, embryonic stem cells, or ESCs, mesenchymal stem cells, or MSCs, and induced pluripotent stem cells, or iPS cells. Pluripotent stem cells are a special cell type that can give rise to other types of cells and are essential for development. The authors describe the strengths and weaknesses of each type of stem cell for regenerative medicine applications. They state that both MSC and iPS types of stem cells have the potential to regenerate tissues among many other therapeutic possibilities. In their article, Zomer and colleagues review the potential for MSCs and iPS cells to reshape the field of regenerative and personal medicine.

Dinosaur egg parataxonomy is a classification system that organizes dinosaur eggs by descriptive features such as shape, size, and shell thickness. Though egg parataxonomy originated in the nineteenth century, Zi-Kui Zhao from Beijing, China, developed a modern parataxonomic system in the late twentieth century. Zhao's system, published in 1975, enabled scientists to organize egg specimens according to observable features, and to communicate their findings. The eggshell protects the developing embryo, enables gas exchange between the embryo and the environment external to the egg, and the internal components of the egg provide nutrients for the embryo. Those external and internal features that support a developing embryo leave their mark on eggshells. Dinosaur egg parataxonomy classifies those characteristics and provides insight into dinosaur egg-laying behaviors, reproductive physiology, and embryonic development.

On the Origin of Mitosing Cells by Lynn Sagan appeared in the March 1967 edition of the Journal of Theoretical Biology. At the time the article was published, Lynn Sagan had divorced astronomer Carl Sagan, but kept his last name. Later, she remarried and changed her name to Lynn Margulis, and will be referred to as such throughout this article. In her 1967 article, Margulis develops a theory for the origin of complex cells that have enclosed nuclei, called eukaryotic cells. She proposes that three organelles: mitochondria, plastids, and basal bodies, which are all parts of eukaryotic cells, were once free-living cells that took residence inside primitive eukaryotic cells. This process Margulis called endosymbiosis. Margulis' theory explained the origin of eukaryote cells, which are the fundamental cell type of most multicellular organisms and form the basis of embryogenesis. After fertilization, embryos develop from a single eukaryotic cell that divides by mitosis.

In 1978, James Kitching discovered two dinosaur embryos in a road-cut talus at Roodraai (Red Bend) in Golden Gate Highlands National Park, South Africa. Kitching assigned the fossilized embryos to the species of long necked herbivores Massospondylus carinatus (longer vertebra) from the Early Jurassic period, between 200 and 183 million years ago. The embryos were partially visible but surrounded by eggshell and rock, called matrix. Kitching said that the eggs were too delicate to remove from the matrix without damage. Twenty-seven years later in 2005, Diane Scott, a member of a team led by Robert Reisz from the University of Toronto in Toronto, Canada, uncovered the two almost complete, well-articulated embryos. Scientists have inferred information from the embryos about Massospondylus dinosaurs' growth, development, and behaviors including parental care, gait, and locomotion.