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Frank Rattray Lillie's research on freemartins from 1914 to 1920 in the US led to the theory that hormones partly caused for sex differentiation in mammals. Although sometimes applied to sheep, goats, and pigs, the term freemartin most often refers to a sterile cow that has external female genitalia and internal male gonads and was born with a normal male twin.
Established in tandem with Singapore's national Biomedical Sciences Initiatives, the Bioethics Advisory Committee (BAC) was established by the Singapore Cabinet in December 2000 to examine the potential ethical, legal, and social issues arising from Singapore's biomedical research sector, and to recommend policy to Singapore's government.
Friedrich Tiedemann studied the anatomy of humans and animals in the nineteenth century in Germany. He published on zoological subjects, on the heart of fish, the anatomy of amphibians and echinoderms, and the lymphatic and respiratory system in birds. In addition to his zoological anatomy, Tiedemann, working with the chemist Leopold Gmelin, published about how the digestive system functioned.
Lynn Petra Alexander Sagan Margulis was an American biologist, whose work in the mid-twentieth century focused on cells living together in a mutually advantageous relationship, studied cells and mitochondria in the US during the second half of the twentieth century. She developed a theory for the origin of eukaryotic cells, that proposed two kinds of structures found in eukaryotic cells mitochondria in animals, and plastids in plantsÑwere once free-living bacteria that lived harmoniously and in close proximity to larger cells, a scenario called symbiosis.
Lysogenic bacteria, or virus-infected bacteria, were the primary experimental models used by scientists working in the laboratories of the Pasteur Institute in Paris, France, during the 1950s and 1960s. Historians of science have noted that the use of lysogenic bacteria as a model in microbiological research influenced the scientific achievements of the Pasteur Institute's scientists.
In the 1990s, Ian Wilmut, Jim McWhir, and Keith Campbell performed experiments while working at the Roslin Institute in Roslin, Scotland. Wilmut, McWhir, and Campbell collaborated with Angelica Schnieke and Alex J. Kind at PPL Therapeutics in Roslin, a company researching cloning and genetic manipulation for livestock. Their experiments resulted in several sheep being born in July 1996, one of which was a sheep named Dolly born 5 July 1996.
"Mitochondrial DNA and Human Evolution" (1987), by Rebecca Louise Cann, Mark Stoneking, and Allan Charles Wilson
In 1987 Rebecca Louise Cann, Mark Stoneking, and Allan Charles Wilson published Mitochondrial DNA and Human Evolution in the journal Nature. The authors compared mitochondrial DNA from different human populations worldwide, and from those comparisons they argued that all human populations had a common ancestor in Africa around 200,000 years ago. Mitochondria DNA (mtDNA) is a small circular genome found in the subcellular organelles, called mitochondria.
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.
Wilhelm Friedrich Phillip Pfeffer studied plants in Germany during the late nineteenth and early twentieth centuries. He started his career as an apothecary, but Pfeffer also studied plant physiology, including how plants move and react to changes in light, temperature, and osmotic pressure. He created the Pfeffer Zelle apparatus, also known as the Pfeffer Cell, to study osmosis in plants. PfefferÕs experiments led to new theories about the structure and development of plants.
The American Eugenics Society (AES) was established in the US by
Madison Grant, Harry H. Laughlin, Henry Crampton, Irving Fisher, and
Henry F. Osborn in 1926 to promote eugenics education programs for
the US public. The AES described eugenics as the study of improving
the genetic composition of humans through controlled reproduction of
different races and classes of people. The AES aided smaller eugenic
efforts such as the Galton Society in New York, New York, and the
The Hayflick Limit is a concept that helps to explain the
mechanisms behind cellular aging. The concept states that a normal human
cell can only replicate and divide forty to sixty times before it
cannot divide anymore, and will break down by programmed cell death
or apoptosis. The concept of the Hayflick Limit revised Alexis
Carrel's earlier theory, which stated that cells can replicate
themselves infinitely. Leonard Hayflick developed the concept while
at the Wistar Institute in Philadelphia,
In 1991, the
United Kingdom established the Human Fertilisation and Embryology
Authority (HFEA) as a response to technologies that used human embryos.
The HFEA is a regulatory power of the Health and Social Services
Department in London, UK, that oversees the implementation of
reproductive technologies and the use of embryos in research within the
United Kingdom. It establishes protocols by which researchers may use
human embryos, develops legislation on how human embryos are stored and
Roy John Britten studied DNA sequences in the US in the second
half of the twentieth century, and he helped discover repetitive
elements in DNA sequences. Additionally, Britten helped propose
models and concepts of gene regulatory networks. Britten studied the
organization of repetitive elements and, analyzing data from the
Human Genome Project, he found that the repetitive elements in DNA
segments do not code for proteins, enzymes, or cellular parts.
Britten hypothesized that repetitive elements helped cause cells to
Theophilus Shickel Painter studied the structure and
function of chromosomes in the US during in the early to mid-twentieth century. Painter worked at
the University of Texas at Austin in Austin, Texas. In the 1920s
and 1930s, Painter studied the chromosomes of the salivary gland
giant chromosomes of the fruit fly (Drosophila
melanogaster), with Hermann J. Muller. Muller and Painter
studied the ability of X-rays to cause changes in the chromosomes
of fruit flies. Painter also studied chromosomes in mammals.
In the second half of the
twentieth century, scientists learned how to clone organisms in some
species of mammals. Scientists have applied somatic cell nuclear transfer to clone human and
mammalian embryos as a means to produce stem cells for laboratory
and medical use. Somatic cell nuclear transfer (SCNT) is a technology applied in cloning, stem cell
research and regenerative medicine. Somatic cells are cells that
have gone through the differentiation process and are not germ
cells. Somatic cells donate their nuclei, which scientists
"Hybrids and Chimeras: A Consultation on the Ethical and Social Implications of Creating Human/Animal Embryos in Research" (2007), by the HFEA
To educate its citizens about research into chimeras made from human and non-human animal cells, the United Kingdom's Human Fertilisation Embryology Authority published the consultation piece Hybrids and Chimeras: A Consultation on the Ethical and Social Implications of Creating Human/Animal Embryos in Research, in 2007.
Dennis Lo, also called Yuk Ming Dennis Lo, is a
professor at the Chinese University of Hong Kong in Hong Kong,
China. In 1997, Lo discovered fetal DNA in maternal
plasma, which is the liquid component of a pregnant woman's
blood. By 2002, Lo distinguished the DNA differences between pregnant women
and their fetuses, enabling scientists to identify fetal DNA in pregnant
women's blood. Lo used his discoveries to develop several
non-invasive and prenatal genetic tests, including tests for blood
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.
The Origin and Behavior of Mutable Loci in Maize, by Barbara McClintock, was published in 1950 in the Proceedings of the National Academy of Sciences of the United States of America. McClintock worked at the Cold Spring Harbor Laboratory in Laurel Hollow, New York, at the time of the publication, and describes her discovery of transposable elements in the genome of corn (Zea mays). Transposable elements, sometimes called transposons or jumping genes, are pieces of the chromosome capable of physically changing positions along the chromosome.
"Transfer of Fetal Cells with Multilineage Potential to Maternal Tissue" (2004), by Kiarash Khosrotehrani et al.
In 2004, a team of researchers at Tufts-New England
Medical Center in Boston, Massachusetts, investigated the fetal
cells that remained in the maternal blood stream after pregnancy.
The results were published in Transfer of Fetal Cells with
Multilineage Potential to Maternal Tissue. The team working on that
research included Kiarash Khosrotehrani, Kirby L. Johnson, Dong
Hyun Cha, Robert N. Salomon, and Diana W. Bianchi. The researchers
reported that the fetal cells passed to a pregnant woman during
Born in Ypsilanti, Michigan, on 2 February 1869, Charles Manning Child was the only surviving child of Mary Elizabeth and Charles Chauncey Child, a prosperous, old New England family. Growing up in Higganum, Connecticut, Child was interested in biology from an early age. He made extensive collections of plants and minerals on his family farm and went on to study biology at Wesleyan University, commuting from his family home. Child received his PhB in 1890 and MS in biology in 1892, and then went on to study in Leipzig after his parents death.
"The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme" (1979), by Stephen J. Gould and Richard C. Lewontin
The Spandrels of San Marco and the Panglossian Paradigm:
A Critique of the Adaptationist Programme, hereafter called
The Spandrels, is an article written by Stephen J. Gould and
Richard C. Lewontin published in the Proceedings of the Royal
Society of London in 1979. The paper emphasizes issues with
what the two authors call adaptationism or the adaptationist
programme as a framework to explain how species and traits evolved. The paper
is one in a series of works in which Gould emphasized the
Harry Hamilton Laughlin helped lead the eugenics
movement in the United States during the early twentieth century.
The US eugenics movement of the early twentieth century sought to
reform the genetic composition of the United States population through
sterilization and other restrictive reproductive measures. Laughlin
worked as superintendent and assistant director of the Eugenics
Research Office (ERO) at Cold Spring Harbor Laboratory in Cold
Spring Harbor, New York, alongside director Charles Davenport.
"Hybrids and Chimeras: A report on the findings of the consultation" by the Human Fertilisation and Embryology Authority in October, 2007
In 2007, the Human Fertilisation and Embryology Authority in London, UK, published Hybrids and Chimeras: A Report on the Findings of the Consultation, which summarized a public debate about research on, and suggested policy for, human animal chimeras. The HFEA formulated the report after conducting a series of surveys and debates from earlier in 2007. The HFEA issued a statement in September 2007, followed by an official report published on 1 October 2007. Their report on human-animal chimeras set a worldwide precedent for discussions of the ethical use of those embryos in labs.
In the case Whitner v. South Carolina in 1997, the South Carolina State Supreme Court defined the concept of a child to include viable fetuses. This allowed grounds for prosecution of a pregnant womanÕs prenatal activity if those activities endangered or could potentially endanger the fetus within her. The case brought the issue of fetal rights versus pregnant womenÕs rights to light.