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Phage Group
The phage group (sometimes called the American Phage Group) was an informal network of biologists centered on Max Delbrück that contributed heavily to bacterial genetics and the origins of molecular biology in the mid-20th century. The phage group takes its name from bacteriophages, the bacteria-infecting viruses that the group used as experimental model organisms. In addition to Delbrück, important scientists associated with the phage group include: Niels Jerne, Salvador Luria, Alfred Hershey, Seymour Benzer, Charles Steinberg, Gunther Stent, James D. Watson, Frank Stahl, and Renato Dulbecco. Origins of the phage group: people, ideas, experiments and personal relationships Bacteriophages had been a subject of experimental investigation since Félix d'Herelle had isolated and developed methods for detecting and culturing them, beginning in 1917. Delbrück, a physicist-turned biologist seeking the simplest possible experimental system to probe the fundamental laws of l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Max Delbrück
Max Ludwig Henning Delbrück (; September 4, 1906 – March 9, 1981) was a German–American biophysicist who participated in launching the molecular biology research program in the late 1930s. He stimulated physical science, physical scientists' interest into biology, especially as to basic research to physically explain genes, mysterious at the time. Formed in 1945 and led by Delbrück along with Salvador Luria and Alfred Hershey, the Phage Group made substantial headway unraveling important aspects of genetics. The three shared the 1969 Nobel Prize in Physiology or Medicine "for their discoveries concerning the replication mechanism and the genetic structure of viruses"."The Nobel Prize in Physiology or Medicine 1969" , Nobel Media AB 2013, ''Nobelprize.org'', Web access November 6, 2013 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Caltech
The California Institute of Technology (branded as Caltech) is a private university, private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of Institute of Technology (United States), institutes of technology in the United States that are devoted to the instruction of pure and applied sciences. The institution was founded as a preparatory and vocational school by Amos G. Throop in 1891 and began attracting influential scientists such as George Ellery Hale, Arthur Amos Noyes, and Robert Andrews Millikan in the early 20th century. The vocational and preparatory schools were disbanded and spun off in 1910, and the college assumed its present name in 1920. In 1934, Caltech was elected to the Association of American Universities, and the antecedents of NASA's Jet Propulsion Laboratory, which Caltech continues to manage and operate, were established between 1936 and 1943 under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Genetic Recombination
Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryotes, genetic recombination during meiosis can lead to a novel set of genetic information that can be further passed on from parents to offspring. Most recombination occurs naturally and can be classified into two types: (1) ''interchromosomal'' recombination, occurring through independent assortment of alleles whose loci are on different but homologous chromosomes (random orientation of pairs of homologous chromosomes in meiosis I); & (2) ''intrachromosomal'' recombination, occurring through crossing over. During meiosis in eukaryotes, genetic recombination involves the pairing of homologous chromosomes. This may be followed by information transfer between the chromosomes. The information transfer may occur without physical exchange (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
James Watson
James Dewey Watson (born April 6, 1928) is an American molecular biology, molecular biologist, geneticist, and zoologist. In 1953, he co-authored with Francis Crick the academic paper in ''Nature (journal), Nature'' proposing the Nucleic acid double helix, double helix structure of the DNA molecule. Watson, Crick and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine "for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material". Watson earned degrees at the University of Chicago (Bachelor of Science, 1947) and Indiana University Bloomington (PhD, 1950). Following a post-doctoral year at the University of Copenhagen with Herman Kalckar and Ole Maaløe, Watson worked at the University of Cambridge's Cavendish Laboratory in England, where he first met his future collaborator Francis Crick. From 1956 to 1976, Watson was on the faculty of the Harvard University Biology Department ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Homologous Recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in Cell (biology), cellular organisms but may be also RNA in viruses). Homologous recombination is widely used by cells to accurately DNA repair, repair harmful DNA breaks that occur on both strands of DNA, known as double-strand breaks (DSB), in a process called homologous recombinational repair (HRR). Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and ovum, egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to Adaptation, adapt during the course of evolution. Homologous recombination is also used in horizontal gene transfer to exchange genetic material between different strains and species ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Hershey–Chase Experiment
The Hershey–Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that helped to confirm that DNA is genetic material. While DNA had been known to biologists since 1869, many scientists still assumed at the time that proteins carried the information for inheritance because DNA appeared to be an inert molecule, and, since it is located in the nucleus, its role was considered to be phosphorus storage. In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not. Hershey and Chase and subsequent discoveries all served to prove that DNA is the hereditary material. Hershey shared the 1969 Nobel Prize in Physiology or Medicine with Max Delbrück and Salvador Luria for their "discoveries concerning the genetic structure of viruses". Historical background In the early twentieth century, biolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Martha Chase
Martha Cowles Chase (November 30, 1927 – August 8, 2003), also known as Martha C. Epstein, was an American geneticist who in 1952, with Alfred Hershey, experimentally helped to confirm that DNA rather than protein is the genetic material of life. Early life and college education Chase was born in 1927 in Cleveland, Ohio. Her father was a Western Reserve University Science Instructor and she grew up with her family in Cleveland Heights, Ohio. After graduating from Cleveland Heights High School, she received a bachelor's degree from the College of Wooster in 1950, then worked as a research assistant before returning to school in 1959 and receiving a PhD in Microbiology from the University of Southern California in 1964. Research and later life In 1950, Chase began working as a research assistant at Cold Spring Harbor Laboratory in the laboratory of bacteriologist and geneticist Alfred Hershey. In 1952, she and Hershey performed the Hershey–Chase experiment, which hel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Nobel Prize In Physiology Or Medicine
The Nobel Prize in Physiology or Medicine () is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, according to Alfred Nobel's 1895 will, are awarded "to those who, during the preceding year, have conferred the greatest benefit to humankind". Nobel Prizes are awarded in the fields of Physics, Medicine or Physiology, Chemistry, Literature, and Peace. The Nobel Prize is presented annually on the anniversary of Alfred Nobel's death, 10 December. As of 2024, 115 Nobel Prizes in Physiology or Medicine have been awarded to 229 laureates, 216 men and 13 women. The first one was awarded in 1901 to the German physiologist, Emil von Behring, for his work on serum therapy and the development of a vaccine against diphtheria. The first woman to receive the Nobel Prize in Physiology or Medicine, Gerty Cori, received it in 1947 for her role in elucida ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Selection (biology)
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with selective breeding, artificial selection, which is intentional, whereas natural selection is not. Genetic diversity, Variation of traits, both Genotype, genotypic and phenotypic, exists within all populations of organisms. However, some traits are more likely to facilitate survival and reproductive success. Thus, these traits are passed the next generation. These traits can also become more Allele frequency, common within a population if the environment that favours these traits remains fixed. If new traits become more favoured due to changes in a specific Ecological niche, niche, microevolution occurs. If new traits become more favoured due to changes in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Mutations
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining), cause an error during other forms of repair, or cause an error during replication ( translesion synthesis). Mutations may also result from substitution, insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce detectable changes in the observable characteristics (phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity. Mutation is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Luria–Delbrück Experiment
The Luria–Delbrück experiment (1943) (also called the Fluctuation Test) demonstrated that in bacteria, genetic mutations arise in the absence of selective pressure rather than being a response to it. Thus, it concluded Darwin's theory of natural selection acting on random mutations applies to bacteria as well as to more complex organisms. Max Delbrück and Salvador Luria won the 1969 Nobel Prize in Physiology or Medicine in part for this work. Simple model Suppose a single bacterium is introduced to a growth medium with rich nutrients, and allowed to grow for N\times of its doubling time, we would obtain 2^N offsprings. Then, we introduce a ''challenge'' by bacteriophages. This would kill off most bacteria, but leave some alive. We can then smear the growth medium over a new growth medium, and count the number of colonies as the number of survivors. In the Lamarckian scenario, each bacterium faces the challenge alone. Most would perish, but a few would survive the ordeal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Lytic Cycle
The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacteriophages that can only go through the lytic cycle are called virulent phages (in contrast to temperate phages). In the lytic cycle, the viral DNA exists as a separate free floating molecule within the bacterial cell, and replicates separately from the host bacterial DNA, whereas in the lysogenic cycle, the viral DNA is integrated into the host genome. This is the key difference between the lytic and lysogenic cycles. However, in both cases the virus/phage replicates using the host DNA machinery. Description The lytic cycle is often separated into six stages: attachment, penetration, transcription, biosynthesis, maturation, and lysis. # Attachment – the phage attaches itself to the surface of the host cell in order to inject its DNA int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
