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Ernest Everett Just (1883-1941)

Ernest Everett Just was an early twentieth century American experimental embryologist involved in research at the Marine Biological Laboratory (MBL) at Woods Hole, Massachusetts, and the Stazione Zoologica in Naples, Italy. Just was known for simple but elegant experiments that supported the "fertilizing" theory of Frank R. Lillie and served as an antagonist to Jacques Loeb's work with artificial parthenogenesis.

Format: Articles

Subject: People

Your Baby’s Sex: Now You Can Choose (1970), by David M. Rorvik and Landrum B. Shettles

In the book Your Baby’s Sex: Now You Can Choose, David Michael Rorvik and Landrum Brewer Shettles describe methods that couples can use prior to and during conception that will increase the chances of producing a child of their desired sex. Rorvik, a science writer, and Shettles, an obstetrics and gynecology researcher and physician, co-wrote the book. Shettles developed the methods detailed in the book during the 1960s. Although the authors claim a high success rate, some researchers have contested the validity of the methods proposed in Your Baby’s Sex: Now You Can Choose.

Format: Articles

Subject: Publications

Alec John Jeffreys (1950–)

Alec John Jeffreys created a process called DNA fingerprinting in the UK during the twentieth century. For DNA fingerprinting, technicians identify a person as the source of a biological sample by comparing the genetic information contained in the person's DNA to the DNA contained in the sample. Jeffreys developed the technique in the 1980s while at the University of Leicester in Leicester, UK. Jeffreys's technique had immediate applications. In forensic science, DNA fingerprinting enabled police to identify suspects of crimes based on their genetic identities.

Format: Articles

Subject: People

The Meselson-Stahl Experiment (1957–1958), by Matthew Meselson and Franklin Stahl

In an experiment later named for them, Matthew Stanley Meselson and Franklin William Stahl in the US demonstrated during the 1950s the semi-conservative replication of DNA, such that each daughter DNA molecule contains one new daughter subunit and one subunit conserved from the parental DNA molecule. The researchers conducted the experiment at California Institute of Technology (Caltech) in Pasadena, California, from October 1957 to January 1958.

Format: Articles

Subject: Processes, Experiments

David Baltimore (1938– )

David Baltimore studied viruses and the immune system in the US during the twentieth century. In 1975, Baltimore was awarded the Nobel Prize in Physiology or Medicine for discovering reverse transcriptase, the enzyme used to transfer information from RNA to DNA. The discovery of reverse transcriptase contradicted the central dogma of biology at the time, which stated that the transfer of information was unidirectional from DNA, RNA, to protein.

Format: Articles

Subject: People

Effects of Prenatal Alcohol Exposure on Cerebellum Development

Prenatal exposure to alcohol (ethanol) results in a continuum of physical, neurological, behavioral, and learning defects collectively grouped under the heading fetal alcohol spectrum disorders (FASD). Fetal alcohol syndrome (FAS) is the most severe combination of these defects under this heading, and is characterized by pre- and postnatal growth deficiencies, facial abnormalities, and defects of the central nervous system (CNS).

Format: Articles

Subject: Disorders, Reproduction

George W. Beadle's One Gene-One Enzyme Hypothesis

The one gene-one enzyme hypothesis, proposed by George Wells Beadle in the US in 1941, is the theory that each gene directly produces a single enzyme, which consequently affects an individual step in a metabolic pathway. In 1941, Beadle demonstrated that one gene in a fruit fly controlled a single, specific chemical reaction in the fruit fly, which one enzyme controlled.

Format: Articles

Subject: Theories

Harald zur Hausen's Experiments on Human Papillomavirus Causing Cervical Cancer (1976–1987)

From 1977 to 1987, Harald zur Hausen led a team of researchers across several institutions in Germany to investigate whether the human papillomavirus (HPV) caused cervical cancer. Zur Hausen's first experiment tested the hypothesis that HPV caused cervical cancer rather than herpes simplex virus type 2 (HSV-2), the then accepted cause. His second and third experiments detailed methods to identify two previously unidentified HPV strains, HPV 16 and HPV 18, in cervical cancer tumor samples. The experiments showed that HPV 16 and 18 DNA were present in cervical tumor samples.

Format: Articles

Subject: Experiments

"Generation of Induced Pluripotent Stem Cells Using Recombinant Proteins" (2009), by Hongyan Zhou et al.

Induced pluripotent stem cells (iPSCs) are studied carefully by scientists not just because they are a potential source of stem cells that circumvents ethical controversy involved with experimentation on human embryos, but also because of their unique potential to advance the field of regenerative medicine. First generated in a lab by Kazutoshi Takahashi and Shinya Yamanaka in 2006, iPSCs have the ability to differentiate into cells of all types.

Format: Articles

Subject: Publications

Purkinje Cells

Purkinje cells, also called Purkinje neurons, are neurons in vertebrate animals located in the cerebellar cortex of the brain. Purkinje cell bodies are shaped like a flask and have many threadlike extensions called dendrites, which receive impulses from other neurons called granule cells. Each cell also has a single projection called an axon, which transmits impulses to the part of the brain that controls movement, the cerebellum. Purkinje cells are inhibitory neurons: they secrete neurotransmitters that bind to receptors that inhibit or reduce the firing of other neurons.

Format: Articles

Subject: Theories

Arthur William Galston (1920–2008)

Arthur W. Galston studied plant hormones in the United States during the late-twentieth century. His dissertation on the flowering process of soybean plants led others to develop Agent Orange, the most widely employed herbicide during the Vietnam War, used to defoliate forests and eliminate enemy cover and food sources. Galston protested the spraying of those defoliants in Vietnam, as they could be harmful to humans, animals, and the environment.

Format: Articles

Subject: People

"Experiments on Artificial Parthenogenesis in Annelids (Chaetopterus) and the Nature of the Process of Fertilization" (1901), by Jacques Loeb

Jacques Loeb showed that scientists could achieve artificial parthenogenesis with some types of annelid worm eggs through a series of experiments in 1900. Loeb published the results of his experiments in 1901 as "Experiments on Artificial Parthenogenesis in Annelids (Chaetopterus) and the Nature of the Process of Fertilization," in The American Journal of Physiology. Loeb 's results broadened the range of animals to which artificial parthenogenesis applied beyond sea urchins.

Format: Articles

Subject: Experiments

Cold Spring Harbor Laboratory (1890- )

Cold Spring Harbor Laboratory (CSHL) is a non-profit research institution that specializes in cancer, neuroscience, plant biology, quantitative biology, and genomics. The organization is located on the shores of Cold Spring Harbor in Laurel Hollow, New York. The Brooklyn Institute of Arts and Sciences established the CSHL in 1890, to provide scientists with facilities to research Charles Darwin's evolutionary theory. The first mission of CSHL was biological science education.

Format: Articles

Subject: Organizations

"Genetic Control of Biochemical Reactions in Neurospora" (1941), by George W. Beadle and Edward L. Tatum

George Wells Beadle and Edward Lawrie Tatum's 1941 article Genetic Control of Biochemical Reactions in Neurospora detailed their experiments on how genes regulated chemical reactions, and how the chemical reactions in turn affected development in the organism. Beadle and Tatum experimented on Neurospora, a type of bread mold, and they concluded that mutations to genes affected the enzymes of organisms, a result that biologists later generalized to proteins, not just enzymes.

Format: Articles

Subject: Experiments

Leon Chesley (1908-2000)

Leon Chesley studied hypertension, or high blood pressure, in pregnant women during the mid-twentieth century. Chesley studied preeclampsia and eclampsia, two hypertensive disorders found in approximately five percent of all US pregnancies. In New Jersey and New York, Chesley devoted over forty years to researching preeclampsia and eclampsia. Chesley conducted several long-term studies using the same group of women beginning from their pregnancies.

Format: Articles

Subject: People, Reproduction

"Generation of Germline-Competent Induced Pluripotent Stem Cells" (2007), by Keisuke Okita, Tomoko Ichisaka, and Shinya Yamanaka

In the July 2007 issue of Nature, Keisuke Okita, Tomoko Ichisaka, and Shinya Yamanaka added to the new work on induced pluripotent stem cells (iPSCs) with their "Generation of Germline-Competent Induced Pluripotent Stem Cells" (henceforth abbreviated "Generation"). The authors begin the paper by noting their desire to find a method for inducing somatic cells of patients to return to a pluripotent state, a state from which the cell can differentiate into any type of tissue but cannot form an entire organism.

Format: Articles

Subject: Publications

Sex-determining Region Y in Mammals

The Sex-determining Region Y (Sry in mammals but SRY in humans) is a gene found on Y chromosomes that leads to the development of male phenotypes, such as testes. The Sry gene, located on the short branch of the Y chromosome, initiates male embryonic development in the XY sex determination system. The Sry gene follows the central dogma of molecular biology; the DNA encoding the gene is transcribed into messenger RNA, which then produces a single Sry protein.

Format: Articles

Subject: Processes

Charles Robert Cantor (1942- )

Charles Robert Cantor helped sequence the human genome, and he developed methods to non-invasively determine the genes in human fetuses. Cantor worked in the US during the twentieth and twenty-first centuries. His early research focused on oligonucleotides, small molecules of DNA or RNA. That research enabled the development of a technique that Cantor subsequently used to describe nucleotide sequences of DNA, a process called sequencing, in humans. Cantor was the principal scientist for the Human Genome Project, for which scientists sequenced the entirety of the human genome in 2003.

Format: Articles

Subject: People, Reproduction

Wilhelm Friedrich Phillip Pfeffer (1845-1920)

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.

Format: Articles

Subject: People

Agent Orange Birth Defects

Sprayed extensively by the US military in Vietnam, Agent Orange contained a dioxin contaminant later found to be toxic to humans. Despite reports by Vietnamese citizens and Vietnam War veterans of increased rates of stillbirths and birth defects in their children, studies in the 1980s showed conflicting evidence for an association between the two. In 1996, the US National Academy of Sciences reported that there was evidence that suggested dioxin and Agent Orange exposure caused spina bifida, a birth defect in which the spinal cord develops improperly.

Format: Articles

Subject: Disorders

Agent Orange as a Cause of Spina Bifida

Spina bifida is a birth defect that affects the spines of developing fetuses and infants, and research in the 20th century indicated that chemicals in the herbicide Agent Orange likely lead to the birth defect. People with spina bifida can have nerve damage, paralysis, and mental disabilities. During the Vietnam War in the 1960s, the US military employed Agent Orange and other herbicides to destroy enemy crops and forest cover until 1970.

Format: Articles

Subject: Disorders

Max Ludwig Henning Delbruck (1906–1981)

Max Ludwig Henning Delbrick applied his knowledge of theoretical physics to biological systems such as bacterial viruses called bacteriophages, or phages, and gene replication during the twentieth century in Germany and the US. Delbrück demonstrated that bacteria undergo random genetic mutations to resist phage infections. Those findings linked bacterial genetics to the genetics of higher organisms. In the mid-twentieth century, Delbrück helped start the Phage Group and Phage Course in the US, which further organized phage research.

Format: Articles

Subject: People

Fetal Alcohol Syndrome (FAS)

The concept Fetal Alcohol Syndrome (FAS) refers to a set of birth defects that occur in children born to mothers who abused alcohol during pregnancy. The alcohol-induced defects include pre- and post-natal growth deficiencies, minor facial abnormalities, and damage to the developing central nervous system (CNS).

Format: Articles

Subject: Disorders

Franklin William Stahl (1929– )

Franklin William Stahl studied DNA replication, bacteriophages, and genetic recombination in the US during the mid-twentieth and early twenty-first centuries. With his colleague Matthew Meselson, Stahl performed an experiment called the Meselson-Stahl experiment, which provided evidence for a process called semi-conservative DNA replication. Semi-conservative replication is a process in which each strand of a parental DNA double helix serves as a template for newly replicated daughter strands, so that one parental strand is conserved in every daughter double helix.

Format: Articles

Subject: People

Meselson, Stahl, and the Replication of DNA: A History of "The Most Beautiful Experiment in Biology" (2001), by Frederic Lawrence Holmes

In 2001, Yale University Press published Frederic Lawrence Holmes' book, Meselson, Stahl, and the Replication of DNA: A History of "The Most Beautiful Experiment in Biology" (Replication of DNA), which chronicles the 1950s debate about how DNA replicates. That experiment verified that DNA replicates semi-conservatively as originally proposed by Watson and Crick. Rather than focusing solely on experiments and findings, Holmes's book presents the investigative processes of scientists studying DNA replication.

Format: Articles

Subject: Publications