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Modifier Gene
Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is dependent on the genetic background in which it appears. Epistatic mutations therefore have different effects on their own than when they occur together. Originally, the term ''epistasis'' specifically meant that the effect of a gene variant is masked by that of a different gene. The concept of ''epistasis'' originated in genetics in 1907 but is now used in biochemistry, computational biology and evolutionary biology. The phenomenon arises due to interactions, either between genes (such as mutations also being needed in Regulation of gene expression, regulators of gene expression) or within them (multiple mutations being needed before the gene loses function), leading to non-linear effects. Epistasis has a great influence on the shape of evol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epistaxis
A nosebleed, also known as epistaxis, is bleeding from the nose. Blood can flow down into the stomach, and cause nausea and vomiting. In more severe cases, blood may come out of both nostrils. Rarely, bleeding may be so significant that low blood pressure occurs. Blood may also come up the nasolacrimal duct and out from the eye. Risk factors include trauma, including putting the finger in the nose, blood thinners, high blood pressure, alcoholism, seasonal allergies, dry weather, and inhaled corticosteroids. There are two types: anterior, which is more common; and posterior, which is less common but more serious. Anterior nosebleeds generally occur from Kiesselbach's plexus while posterior bleeds generally occur from the sphenopalatine artery. The diagnosis is by direct observation. Prevention may include the use of petroleum jelly in the nose. Initially, treatment is generally the application of pressure for at least five minutes over the lower half of the nose. If this is no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Bateson
William Bateson (8 August 1861 – 8 February 1926) was an English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscovery in 1900 by Hugo de Vries and Carl Correns. His 1894 book ''Materials for the Study of Variation'' was one of the earliest formulations of the new approach to genetics. Early life and education Bateson was born 1861 in Whitby on the Yorkshire coast, the son of William Henry Bateson, Master of St John's College, Cambridge. He was educated at Rugby School and at St John's College, where he graduated BA in 1883 with a first in natural sciences. Taking up embryology, he went to the United States to investigate the development of ''Balanoglossus'', a worm-like hemichordate which led to his interest in vertebrate origins. In 1883–4 he worked in the laboratory of William Keith Brooks, at the Chesapeake Zoölogical Laboratory in Hampton, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantitative Trait Loci
A quantitative trait locus (QTL) is a locus (section of DNA) that correlates with variation of a quantitative trait in the phenotype of a population of organisms. QTLs are mapped by identifying which molecular markers (such as SNPs or AFLPs) correlate with an observed trait. This is often an early step in identifying the actual genes that cause the trait variation. Definition A quantitative trait locus (QTL) is a region of DNA which is associated with a particular phenotypic trait, which varies in degree and which can be attributed to polygenic effects, i.e., the product of two or more genes, and their environment. . These QTLs are often found on different chromosomes. The number of QTLs which explain variation in the phenotypic trait indicates the genetic architecture of a trait. It may indicate that plant height is controlled by many genes of small effect, or by a few genes of large effect. Typically, QTLs underlie continuous traits (those traits which vary continuously, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Biology
Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physical structure of biological macromolecules is known as molecular biology. Molecular biology was first described as an approach focused on the underpinnings of biological phenomena - uncovering the structures of biological molecules as well as their interactions, and how these interactions explain observations of classical biology. In 1945 the term molecular biology was used by physicist William Astbury. In 1953 Francis Crick, James Watson, Rosalind Franklin, and colleagues, working at Medical Research Council unit, Cavendish laboratory, Cambridge (now the MRC Laboratory of Molecular Biology), made a double helix model of DNA which changed the entire research scenario. They proposed the DNA structure based on previous research done by Ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Locus (genetics)
In genetics, a locus (plural loci) is a specific, fixed position on a chromosome where a particular gene or genetic marker is located. Each chromosome carries many genes, with each gene occupying a different position or locus; in humans, the total number of protein-coding genes in a complete haploid set of 23 chromosomes is estimated at 19,000–20,000. Genes may possess multiple variants known as alleles, and an allele may also be said to reside at a particular locus. Diploid and polyploid cells whose chromosomes have the same allele at a given locus are called homozygous with respect to that locus, while those that have different alleles at a given locus are called heterozygous. The ordered list of loci known for a particular genome is called a gene map. Gene mapping is the process of determining the specific locus or loci responsible for producing a particular phenotype or biological trait. Association mapping, also known as "linkage disequilibrium mapping", is a method of ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interaction
Interaction is action that occurs between two or more objects, with broad use in philosophy and the sciences. It may refer to: Science * Interaction hypothesis, a theory of second language acquisition * Interaction (statistics) * Interactions of actors theory, created by cybernetician Gordon Pask * Fundamental interaction, in physics * Human–computer interaction * Social interaction between people Biology * Biological interaction * Cell–cell interaction * Drug interaction * Gene–environment interaction * Protein–protein interaction Chemistry * Aromatic interaction * Cation-pi interaction * Metallophilic interaction Arts and media * Interaction (album), ''Interaction'' (album), 1963, by Art Farmer's Quartet * ACM Interactions, ACM ''Interactions'', a magazine published by the Association for Computing Machinery * Interactions (The Spectacular Spider-Man), "Interactions" (''The Spectacular Spider-Man''), an episode of the animated television series * 63rd World Science F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dominance (genetics)
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new (''de novo'') or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes ( autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child (see Sex linkage). Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance such as incomplete d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Hair
Brown hair, also referred to as brunet (male) or brunette (female), is the second most common human hair color, after black hair. It varies from light brown to a medium dark hair. It is characterized by higher levels of the dark pigment eumelanin and lower levels of the pale pigment pheomelanin. Brown hair is common among populations in the Western world, especially among those from Northwestern Europe, Central Europe, Southeastern Europe, Eastern Europe, Southern Europe, Southern Cone,Brazil, Colombia, Costa Rica, Puerto Rico and the United States, and also some populations in the Middle East where it transitions smoothly into black hair.Frost, Peter"Why Do Europeans Have So Many Hair and Eye Colors?"(summarizing Frost, P. 2006. European hair and eye color - A case of frequency-dependent sexual selection? Evolution and Human Behavior 27:85-103) Additionally, brown hair is common among Australian Aboriginals and Melanesians. Etymology and grammar The term ''brunette'' is the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alopecia Totalis
Alopecia totalis is the loss of all hair on the head and face. Its causes are unclear, but believed to be autoimmune. Research suggests there may be a genetic component linked to developing alopecia totalis; the presence of DRB1*0401 and DQB1*0301, both of which are Human Leukocyte Antigens (HLA), were found to be associated with long-standing alopecia totalis. Treatment Methotrexate and corticosteroids are proposed treatments. Scalp cooling has specifically been used to prevent alopecia in docetaxel chemotherapy, although it has been found prophylactic in other regimens as well. Treatment effects may take time to resolve, with one study showing breast cancer survivors wearing wigs up to 2 years after chemotherapy. See also *Alopecia areata *Alopecia universalis __NOTOC__ Alopecia universalis (AU), also known as alopecia areata universalis, is a medical condition involving the loss of all body hair, including eyebrows, eyelashes, chest hair, armpit hair, and pubic hair. It is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypostatic Gene
A hypostatic gene is one whose phenotype is altered by the expression of an allele at a separate locus, in an epistasis event. Example: In labrador retrievers, the chocolate coat colour is a result of homozygosity for a gene that is epistatic to the "black vs. brown" gene. The alleles determining whether the dog is black or brown, are that of the ''hypostatic gene'' in this event. See also * Epistasis Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is dep ... * Bombay phenotype References Further reading {{cite book , last = Hartwell , first = Leland , author2=L. Hood , author3=M. Goldberg , author4=A. Reynolds , author5=L. Silver , author6=R. Veres , title = Genetics: From Genes to Genomes , publisher = McGraw-Hill , date = 2004 , location = New York, NY , pag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Classical Genetics
Classical genetics is the branch of genetics based solely on visible results of reproductive acts. It is the oldest discipline in the field of genetics, going back to the experiments on Mendelian inheritance by Gregor Mendel who made it possible to identify the basic mechanisms of heredity. Subsequently, these mechanisms have been studied and explained at the molecular level. Classical genetics consists of the techniques and methodologies of genetics that were in use before the advent of molecular biology. A key discovery of classical genetics in eukaryotes was genetic linkage. The observation that some genes do not segregate independently at meiosis broke the laws of Mendelian inheritance and provided science with a way to map characteristics to a location on the chromosomes. Linkage maps are still used today, especially in breeding for plant improvement. After the discovery of the genetic code and such tools of cloning as restriction enzymes, the avenues of investigation open ... [...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] |
