Embryo Project Encyclopedia Articles

Calvin Blackman Bridges studied chromosomes and heredity in the US throughout the early twentieth century. Bridges performed research with Thomas Hunt Morgan at Columbia University in New York City, New York, and at the California Institute of Technology in Pasadena, California. Bridges and Morgan studied heredity in Drosophila, the common fruit fly. Throughout the early twentieth century, researchers were gathering evidence that genes, or what Gregor Mendel had called the factors that control heredity, are located on chromosomes. At Columbia, Morgan disputed the theory, but in 1916, Calvin Bridges published evidence that, according to Morgan, did much to convince skeptics of that theory. Bridges also established that specific chromosomes function in determining sex in Drosophila.

Matthew Kaufman was a professor of anatomy at the University of Edinburgh, in Edinburgh, UK, who specialized in mouse anatomy, development, and embryology during the late twentieth century. According to the The Herald, he was the first, alongside his colleague Martin Evans, to isolate and culture embryonic stem cells. Researchers initially called those cells Evans-Kaufman cells. In 1992, Kaufman published The Atlas of Mouse Development, a book that included photographs of mice development and mice organs over time. Kaufman also wrote books about UK medical history, phrenology, or the study of craniums as an indicator of character or mental ability, and medical teaching in the eighteenth and nineteenth centuries. Kaufman’s anatomical records and experiments in mouse development contributed to genetic engineering, embryology, and anatomy.

In 2012, Jennifer Doudna, Emmanuelle Charpentier from the University of California, Berkeley, in Berkeley, California, and Umeå University in Umeå, Sweden, along with their colleagues discovered how bacteria use the CRISPR/cas 9 system to protect themselves from viruses. The researchers also proposed the idea of using the CRISPR/cas 9 system as a genome editing tool. In bacteria and archaea, researchers had found that CRISPR, which stands for clustered regularly interspaced short palindromic repeats, and CRISPR associated proteins, or cas, helped organisms recognize and silence the genetic material of viruses that have infected the cell before. In their experiment, Doudna, Charpentier, and their colleagues found how the specific molecules in bacteria can recognize and cut specific DNA sequences of invading viruses. Doudna, Charpentier, and their colleagues’ discovery of the CRISPR/cas 9 mechanism and proposal of using CRISPR/cas 9 for genetic editing led to the successful engineering of CRISPR/cas 9 as a novel method of editing genomes.

Alfred Henry Sturtevant studied heredity in fruit flies in the US throughout the twentieth century. From 1910 to 1928, Sturtevant worked in Thomas Hunt Morgan’s research lab in New York City, New York. Sturtevant, Morgan, and other researchers established that chromosomes play a role in the inheritance of traits. In 1913, as an undergraduate, Sturtevant created one of the earliest genetic maps of a fruit fly chromosome, which showed the relative positions of genes along the chromosome. At the California Institute of Technology in Pasadena, California, he later created one of the first fate maps, which tracks embryonic cells throughout their development into an adult organism. Sturtevant’s contributions helped scientists explain genetic and cellular processes that affect early organismal development.

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. Later in their careers, both Hölldobler and Wilson argued that kin selection theory provided an insufficient explanation for the evolution of social behavior. Hölldobler and Wilsons' efforts were emblematic of a larger trend among ant researchers and sociobiologists to explain the evolution of social behavior by focusing on the reproductive dynamics of social organisms.

Wilhelm Pfeffer published his book Osmotische Untersuchungen: Studien Zur Zellmechanik (Osmotic Investigations: Studies on Cell Mechanics) in 1877 during his time as a professor of botany at the University of Basel in Basel, Switzerland. Gordon R. Kepner and Eduard J. Stadelmann translated the book into English in 1985. Verlag von Wilhelm Engelmann in Leipzig, Germany, published the original book in German in 1877 and Van Nostrand Reinhold Company in New York, New York, published the English version in 1985. The book focuses on the cell mechanics of osmotic processes to explain why high pressure exists in plant cells. The book also provides one of the earliest detailed descriptions of the Pfeffer Cell, a devise Pfeffer had created to model and study osmosis in plant cells. The model helped Pfeffer propose theories for how osmosis affected metabolism, growth, and development of plant cells.

The Human Papillomavirus (HPV) strains 16 and 18 are the two most common HPV strains that lead to cases of genital cancer. HPV is the most commonly sexually transmitted disease, resulting in more than fourteen million cases per year in the United States alone. When left untreated, HPV leads to high risks of cervical, vaginal, vulvar, anal, and penile cancers. In 1983 and 1984 in Germany, physician Harald zur Hausen found that two HPV strains, HPV-16 and HPV-18, caused cervical cancer in women. In the early twenty first century, pharmaceutical companies Merck & Co. and GlaxoSmithKline created HPV vaccines protecting against HPV-16 and HPV-18, which have reduced the number of HPV infections by fifty-six percent in the US. Discovering HPV strains 16 and 18 allowed physicians to test for those cancer-causing cell populations using Pap smears, a diagnostic tool that collects cells from the woman's cervix to identify cancerous cases of HPV infection. By identifying the cancerous strains of HPV-16 and HPV-18 and utilizing preventative measures such as the Pap smear and HPV vaccines, the rates of cervical cancer and other HPV-related cancers have reduced.

In the 1936 case United States v. One Package of Japanese Pessaries, the US Court of Appeals for the Second Circuit in New York City, New York, confirmed that physicians had the right to distribute contraceptives to patients for medical purposes. In January 1933, US Customs confiscated a package of contraceptives imported from Japan by US physician Hannah Stone. They claimed that the package violated section 305 of the Tariff Act of 1930, which, like the 1873 anti-obscenity Comstock Act, granted the US government authority to seize contraceptive materials imported into the country or sent through the mail. The court ruled that US Customs was not justified in confiscating the package and ordered its return to Stone. United States v. One Package exempted physicians from the restrictions surrounding the distribution of contraceptives and contributed to the subsequent dismantling of the Comstock Act in later court cases.

Matthias Jacob Schleiden helped develop the cell theory in Germany during the nineteenth century. Schleiden studied cells as the common element among all plants and animals. Schleiden contributed to the field of embryology through his introduction of the Zeiss microscope lens and via his work with cells and cell theory as an organizing principle of biology.

From 1913 to 1916, Calvin Bridges performed experiments that indicated genes are found on chromosomes. His experiments were a part of his doctoral thesis advised by Thomas Hunt Morgan in New York, New York. In his experiments, Bridges studied Drosophila, the common fruit fly, and by doing so showed that a process called nondisjunction caused chromosomes, under some circumstances, to fail to separate when forming sperm and egg cells. Nondisjunction, as described by Bridges, caused sperm or egg cells to contain abnormal amounts of chromosomes. In some cases, that caused the offspring produced by the sperm or eggs to display traits that they would typically not have. His research on nondisjunction provided evidence that chromosomes carry genetic traits, including those that determine the sex of an organism.