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Transformation (genetics)
In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s). For transformation to take place, the recipient bacterium must be in a state of competence, which might occur in nature as a time-limited response to environmental conditions such as starvation and cell density, and may also be induced in a laboratory. Transformation is one of three processes that lead to horizontal gene transfer, in which exogenous genetic material passes from one bacterium to another, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium). In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium. As of 2014 about 8 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Malignant Transformation
Malignant transformation is the process by which cells acquire the properties of cancer. This may occur as a primary process in normal tissue, or secondarily as ''malignant degeneration'' of a previously existing benign tumor. Causes There are many causes of primary malignant transformation, or tumorigenesis. Most human cancers in the United States are caused by external factors, and these factors are largely avoidable. These factors were summarized by Doll and Peto in 1981, and were still considered to be valid in 2015. These factors are listed in the table. a Reproductive and sexual behaviors include: number of partners; age at first menstruation; zero versus one or more live births Examples of diet-related malignant transformation Diet and colon cancer Colon cancer provides one example of the mechanisms by which diet, the top factor listed in the table, is an external factor in cancer. The Western diet of African Americans in the United States is associated with a ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Escherichia Coli
''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly found in the lower intestine of warm-blooded organisms. Most ''E. coli'' strains are part of the normal microbiota of the gut, where they constitute about 0.1%, along with other facultative anaerobes. These bacteria are mostly harmless or even beneficial to humans. For example, some strains of ''E. coli'' benefit their hosts by producing vitamin K2 or by preventing the colonization of the intestine by harmful pathogenic bacteria. These mutually beneficial relationships between ''E. coli'' and humans are a type of mutualistic biological relationship—where both the humans and the ''E. coli'' are benefitting each other. ''E. coli'' is expelled into the environment within fecal matter. The bacterium grows massi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joshua Lederberg
Joshua Lederberg (May 23, 1925 – February 2, 2008) was an American molecular biology, molecular biologist known for his work in microbial genetics, artificial intelligence, and the United States space program. He was 33 years old when he won the 1958 Nobel Prize in Physiology or Medicine for discovering that bacteria can mate and exchange genes (bacterial conjugation). He shared the prize with Edward Tatum and George Beadle, who won for their work with genetics. In addition to his contributions to biology, Lederberg did extensive research in artificial intelligence. This included work in the NASA experimental programs seeking life on Mars and the chemistry expert system Dendral. Early life and education Lederberg was born in Montclair, New Jersey, to a Jewish family, son of Esther Goldenbaum Schulman Lederberg and Rabbi Zvi Hirsch Lederberg, in 1925, and moved to Washington Heights, Manhattan as an infant. He had two younger brothers. Lederberg graduated from Stuyvesant High S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transduction (genetics)
Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector. An example is the viral transfer of DNA from one bacterium to another and hence an example of horizontal gene transfer. Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant ( transformation is susceptible to DNase). Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome (both bacterial and mammalian cells). Discovery (bacterial transduction) Transduction was discovered in ''Salmonella'' by Norton Zinder and Joshua Lederberg at the University of Wisconsin–Madison in 1952. In the lytic and lysogenic cycles Transduction happens through either the lytic cycle or the lysogenic cycle. When bacteriophages (viruses that infect bacteria) that are lytic infect bacterial cells, they harness the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Markers
A genetic marker is a gene or DNA sequence with a known location on a chromosome that can be used to identify individuals or species. It can be described as a variation (which may arise due to mutation or alteration in the genomic loci) that can be observed. A genetic marker may be a short DNA sequence, such as a sequence surrounding a single base-pair change (single nucleotide polymorphism, SNP), or a long one, like minisatellites. Background For many years, gene mapping was limited to identifying organisms by traditional phenotypes markers. This included genes that encoded easily observable characteristics, such as blood types or seed shapes. The insufficient number of these types of characteristics in several organisms limited the possible mapping efforts. This prompted the development of gene markers, which could identify genetic characteristics that are not readily observable in organisms (such as protein variation). Types Some commonly used types of genetic markers are: * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maclyn McCarty
Maclyn McCarty (June 9, 1911 – January 2, 2005) was an American geneticist, a research scientist described in 2005 as "the last surviving member of a Manhattan scientific team that overturned medical dogma in the 1940s and became the first to demonstrate that genes were made of DNA." He had worked at Rockefeller University "for more than 60 years." 1994 marked 50 years since this work's release. McCarty devoted his life as a physician-scientist to studying infectious disease organisms, and was best known for his part in the monumental discovery that DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ..., rather than protein, constituted the chemical nature of a gene. Uncovering the molecular secret of the gene in question — that for the capsular polysaccharide of pneumococcal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colin Munro MacLeod
Colin Munro MacLeod (January 28, 1909 – February 11, 1972) was a Canadian-American geneticist. He was one of a trio of scientists who discovered that deoxyribonucleic acid, or DNA is responsible for the transformation of the physical characteristics of bacteria, which subsequently led to its identification as the molecule responsible for heredity. Biography MacLeod was born in Port Hastings, Nova Scotia, Canada, one of eight children of a schoolteacher and a Scottish Presbyterian minister. He entered McGill University at the age of 16 after skipping three grades in primary school, and completed his medical studies by age 23. In his early years as a research scientist, MacLeod, with Oswald Avery and Maclyn McCarty, demonstrated DNA is the molecule responsible for bacterial transformation — and in retrospect, the physical basis of the gene. In 1941, Avery and MacLeod separated a crude extract from smooth ('S') strains of ''Streptococcus pneumoniae'', the most co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oswald Avery
Oswald Theodore Avery Jr. (October 21, 1877 – February 20, 1955) was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller Hospital in New York City. Avery was one of the first molecular biologists and a pioneer in immunochemistry, but he is best known for the experiment (published in 1944 with his co-workers Colin MacLeod and Maclyn McCarty) that isolated DNA as the material of which genes and chromosomes are made. The Nobel laureate Arne Tiselius said that Avery was the most deserving scientist not to receive the Nobel Prize for his work, though he was nominated for the award throughout the 1930s, 1940s, and 1950s. The lunar crater Avery was named in his honor. Family Oswald Avery's grandfather was Joseph Henry Avery. He was a papermaker, and he was in charge of the papermaking at Oxford University. He discovered a way to make thin paper that could be printed on both sides. This paper was used to make O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Griffith's Experiment
Griffith's experiment, performed by Frederick Griffith and reported in 1928, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation. Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic information. Pneumonia was a serious cause of death in the wake of the post-WWI Spanish influenza pandemic, and Griffith was studying the possibility of creating a vaccine. Griffith used two strains of pneumococcus ('' Diplococcus pneumoniae'') bacteria which infect mice – a type III-S (smooth) which was virulent, and a type II-R (rough) strain which was nonvirulent. The III-S strain synthesized a polysaccharide capsule that protected itself from the host's immune system, resulting in the death of the host, while the II-R strain did not have that protective capsule and was defeated by the host's immune system. A Germ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virulence
Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most cases, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to cause disease—is determined by its virulence factors. In the specific context of gene for gene systems, often in plants, virulence refers to a pathogen's ability to infect a resistant host. Virulence can also be transferred using a plasmid. The noun ''virulence'' (Latin noun ) derives from the adjective ''virulent'', meaning disease severity. The word ''virulent'' derives from the Latin word ''virulentus'', meaning "a poisoned wound" or "full of poison". The term ''virulence'' does not only apply to viruses. From an ecological standpoint, virulence is the loss of fitness induced by a parasite upon its host. Virulence can be understood in terms of proximate causes—those specific traits of the pathogen that help make the host ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
