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Robert W. Allard
Robert Wayne Allard (September 3, 1919 – March 25, 2003) was an American plant breeder and plant population geneticist who is widely regarded as one of the leading plant population geneticists of the 20th century. Allard became Chair of the Genetics Department at University of California, Davis in 1967; he was elected to the National Academy of Sciences in 1973, and was awarded the DeKalb-Pfizer Distinguished Career Award and the Crop Science Science of America Award. He was honored as the Nilsson-Ehle Lecturer of the Mendelian Society of Sweden and as the Wilhelmine Key lecturer of the American Genetic Association. He also served as president of the Genetics Society of America, the American Genetic Association and the American Society of Naturalists. As Chair of the Department of Genetics at U.C. Davis he played a major role in bringing Theodosius Dobzhansky and Francisco J. Ayala to the Genetics Department in the early 1970s. With G. Ledyard Stebbins there as well, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Fernando Valley, California
The San Fernando Valley, known locally as the Valley, is an urbanized valley in Los Angeles County, California. Located to the north of the Los Angeles Basin, it contains a large portion of the City of Los Angeles, as well as unincorporated areas and the incorporated cities of Burbank, Calabasas, Glendale, Hidden Hills, and San Fernando. The valley is well known for its iconic film studios such as Warner Bros. Studio and Walt Disney Studios. In addition, it is home to the Universal Studios Hollywood theme park. Geography The San Fernando Valley is about bound by the Santa Susana Mountains to the northwest, the Simi Hills to the west, the Santa Monica Mountains and Chalk Hills to the south, the Verdugo Mountains to the east, and the San Gabriel Mountains to the northeast. The northern Sierra Pelona Mountains, northwestern Topatopa Mountains, southern Santa Ana Mountains, and Downtown Los Angeles skyscrapers can be seen from higher neighborhoods, passes, roads, and parks i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytogenetics
Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology (a subdivision of human anatomy), that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis. Techniques used include karyotyping, analysis of G-banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescent ''in situ'' hybridization (FISH) and comparative genomic hybridization (CGH). History Beginnings Chromosomes were first observed in plant cells by Carl Nägeli in 1842. Their behavior in animal (salamander) cells was described by Walther Flemming, the discoverer of mitosis, in 1882. The name was coined by another German anatomist, von Waldeyer in 1888. The next stage took place after the development of genetics in the early 20th century, when it was appreciated that the set of chromosomes (the karyotype) was the carrier of the genes. Levitsky seems to have been t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene–environment Interaction
Gene–environment interaction (or genotype–environment interaction or G×E) is when two different genotypes respond to environmental variation in different ways. A norm of reaction is a graph that shows the relationship between genes and environmental factors when phenotypic differences are continuous. They can help illustrate GxE interactions. When the norm of reaction is not parallel, as shown in the figure below, there is a gene by environment interaction. This indicates that each genotype responds to environmental variation in a different way. Environmental variation can be physical, chemical, biological, behavior patterns or life events. Gene–environment interactions are studied to gain a better understanding of various phenomena. In genetic epidemiology, gene–environment interactions are useful for understanding some diseases. Sometimes, sensitivity to environmental risk factors for a disease are inherited rather than the disease itself being inherited. Individual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Selection
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 heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with selective breeding, artificial selection, which in his view is intentional, whereas natural selection is not. Genetic diversity, Variation exists within all populations of organisms. This occurs partly because random mutations arise in the genome of an individual organism, and their offspring can inherit such mutations. Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits. The environment of a genome includes the molecular biology in the Cell (biology), cell, other cells, other individuals, populations, species, as well as the abiotic environment. Because individuals with certain variants of the trait tend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mating System
A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mating, mate under which circumstances. Recognised systems include monogamy, polygamy (which includes polygyny, polyandry, and polygynandry), and promiscuity, all of which lead to different mate choice outcomes and thus these systems affect how sexual selection works in the species which practice them. In plants, the term refers to the degree and circumstances of outcrossing. In human sociobiology, the terms have been extended to encompass the formation of relationships such as marriage. In plants The primary mating systems in plants are outcrossing (cross-fertilisation), autogamy (self-fertilisation) and apomixis (asexual reproduction without fertilization, but only when arising by modification of sexual function). Mixed mating systems, in which plants use two or even all three ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ledyard Stebbins
George Ledyard Stebbins Jr. (January 6, 1906 – January 19, 2000) was an American botany, botanist and geneticist who is widely regarded as one of the leading evolutionary biology, evolutionary biologists of the 20th century. Stebbins received his Ph.D. in botany from Harvard University in 1931. He went on to the University of California, Berkeley, where his work with E. B. Babcock on the genetic evolution of plant species, and his association with a group of evolutionary biologists known as the Bay Area Biosystematists, led him to develop a comprehensive synthesis of plant evolution incorporating genetics. His most important publication was ''Variation and Evolution in Plants'', which combined genetics and Charles Darwin, Darwin's theory of natural selection to describe plant speciation. It is regarded as one of the main publications which formed the core of the Modern synthesis (20th century), modern synthesis and still provides the conceptual framework for research in plant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avena Fatua
''Avena'' is a genus of Eurasian and African plants in the Poaceae, grass family. Collectively known as the oats, they include some species which have been cultivated for thousands of years as a food source for humans and livestock. They are widespread throughout Europe, Asia and northwest Africa. Several species have become naturalized in many parts of the world, and are regarded as invasive weeds where they compete with crop production. All oats have edible seeds, though they are small and hard to harvest in most species. * See Oat for a more detailed discussion of the oat as a food source. Ecology ''Avena'' species, including cultivated oats, are used as food plants by the larvae of some Lepidoptera species, including rustic shoulder-knot and setaceous Hebrew character. For diseases of oats, see List of oat diseases. Species Cultivated oats One species is of major commercial importance as a cereal grain. Four other species are grown as crops of minor or regional impor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Avena Barbata
''Avena barbata'' is a species of wild oat known by the common name slender wild oat. It has edible seeds. It is a diploidized autotetraploid grass (2n=4x=28). Its diploid ancestors are ''A. hirtula'' Lag. and ''A. wiestii'' Steud (2n=2x=14), which are considered Mediterranean and desert ecotypes, respectively, comprising a single species. ''A westie'' and ''A. hirtula'' are widespread in the Mediterranean Basin, growing in mixed stands with ''A. barbata'', though they are difficult to tell apart. This is a winter annual grass with thin tillers (stems) growing up to 60 to 80 centimeters in maximum height, but known to sometimes grow taller. The bristly spikelets are 2 to 3 centimeters long, not counting the bent awn which is up to 4 centimeters in length. ''Avena barbata'' largely reproduces by selfing in natural populations, with very low rates of outcrossing. ''A. barbata'' is native to central Asia (as far east as Pakistan) and the Mediterranean Basin. As an introduced spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collinsia
''Collinsia'' is a genus of about 20 species of annual flowering plants, consisting of the blue eyed Marys and the Chinese houses. It was traditionally placed in the snapdragon family Scrophulariaceae, but following recent research in molecular genetics, it has now been placed in a much enlarged family Plantaginaceae. The genus is endemic to North America, and is named in honor of Zacchaeus Collins, a Philadelphia botanist of the late eighteenth/early nineteenth century. Many of the 20 species may be found in California. Two species, ''Collinsia parviflora'' (smallflower blue eyed Mary) and ''Collinsia violacea'' (violet blue eyed Mary), had medicinal uses among American Indian peoples. Species include: *''Collinsia antonina'' *''Collinsia bartsiifolia'' *'' Collinsia callosa'' *'' Collinsia childii'' *''Collinsia concolor'' *''Collinsia corymbosa'' *''Collinsia grandiflora'' *''Collinsia greenei'' *''Collinsia heterophylla'' *''Collinsia linearis'' *''Collinsia multicolor' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inbreeding
Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and other consequences that may arise from expression of deleterious or recessive traits resulting from incestuous sexual relationships and consanguinity. Animals avoid incest only rarely. Inbreeding results in homozygosity, which can increase the chances of offspring being affected by recessive traits. In extreme cases, this usually leads to at least temporarily decreased biological fitness of a population (called inbreeding depression), which is its ability to survive and reproduce. An individual who inherits such deleterious traits is colloquially referred to as ''inbred''. The avoidance of expression of such deleterious recessive alleles caused by inbreeding, via inbreeding avoidance mechanisms, is the main selective reason for outcrossin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Genetics
Population genetics is a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure. Population genetics was a vital ingredient in the emergence of the modern evolutionary synthesis. Its primary founders were Sewall Wright, J. B. S. Haldane and Ronald Fisher, who also laid the foundations for the related discipline of quantitative genetics. Traditionally a highly mathematical discipline, modern population genetics encompasses theoretical, laboratory, and field work. Population genetic models are used both for statistical inference from DNA sequence data and for proof/disproof of concept. What sets population genetics apart from newer, more phenotypic approaches to modelling evolution, such as evolutionary game theory and adaptive dynamics, is its emphasis on such genetic phenomena as dominance, epi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley production is used as animal fodder, while 30% as a source of fermentable material for beer and certain distilled beverages, and as a component of various foods. It is used in soups and stews, and in barley bread of various cultures. Barley grains are commonly made into malt in a traditional and ancient method of preparation. In 2017, barley was ranked fourth among grains in quantity produced () behind maize, rice and wheat. Etymology The Old English word for barley was ', which traces back to Proto-Indo-European and is cognate to the Latin word ' "flour" (''see corresponding entries''). The direct ancestor of modern English ''barley'' in Old English was the derived adjective ''bærlic'', meaning "of barley". The first citation of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
