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Concerted Evolution
Concerted Evolution- A definition Concerted evolution is the phenomenon where paralogous genes within one species are more closely related to one another than to members of the same gene family in closely related species. In other terms, when specific members of a family are investigated, a greater amount of similarity is found within a species rather than between species. This is suggesting that members within this family do not in fact evolve independently of one another. The concept of concerted evolution is a molecular process which leads to the homogenization of DNA sequences. As shown from the diagram on the right, as each organism evolves, it creates a species that is more closely related to their genes than anyone else in their species. This is demonstrated by the different colors of circles. If each different color is representing a different organism in one species, this is showing that once the blue and the orange reproduce, they create organisms that are incredibl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Theory Of Concerted Evolution- A Molecular Process An Organism May Go Through
''The'' () is a grammatical Article (grammar), article in English language, English, denoting persons or things already mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the Most common words in English, most frequently used word in the English language; studies and analyses of texts have found it to account for seven percent of all printed English-language words. It is derived from gendered articles in Old English which combined in Middle English and now has a single form used with pronouns of any gender. The word can be used with both singular and plural nouns, and with a noun that starts with any letter. This is different from many other languages, which have different forms of the definite article for different genders or numbers. Pronunciation In most dialects, "the" is pronounced as (with the voiced dental fricative followed by a schwa) when followed by a consonant s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Short Interspersed Element
Retrotransposons (also called Class I transposable elements or transposons via RNA intermediates) are a type of genetic component that copy and paste themselves into different genomic locations (transposon) by converting RNA back into DNA through the reverse transcription process using an RNA transposition intermediate. Through reverse transcription, retrotransposons amplify themselves quickly to become abundant in eukaryotic genomes such as maize (49–78%) and humans (42%). They are only present in eukaryotes but share features with retroviruses such as HIV, for example, discontinuous reverse transcriptase-mediated extrachromosomal recombination. These retrotransposons are regulated by a family of short non-coding RNAs termed as PIWI -element induced wimpy testisinteracting RNAs (piRNAs). piRNA is a recently discovered class of ncRNAs, which are in the length range of ~24-32 nucleotides. Initially, piRNAs were described as repeat-associated siRNAs (rasiRNAs) because of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Podisma Pedestris
''Podisma pedestris'' is a species of 'short-horned grasshoppers' belonging to the family Acrididae subfamily Melanoplinae. Distribution This small wingless grasshopper is present in most of Europe and in eastern Palearctic realm through to temperate, mainland east Asia. Description The adult males grow up to long, while the females reach of length. They can be encountered from mid June through October in dry meadows, in rocky slopes of mountains, alpine pastures and forest clearings. They feed on grasses and herbaceous plants. The females lay their eggs on the ground. The basic coloration of the body varies from dark-brownish to yellowish, with black and yellow trasversal stripes on the sides of the abdomen. The males have brighter and more intense colours and more extensive black markings than the females. A dark longitudinal stripe runs from the eye to pronotum. The femora of the hind legs are reddish, while tibiae are bluish with white spines. In both sexes the vestigi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mus Musculus
Mus or MUS may refer to: Abbreviations * MUS, the NATO country code for Mauritius * MUS, the IATA airport code for Minami Torishima Airport * MUS, abbreviation for the Centre for Modern Urban Studies on Campus The Hague, Leiden University, Netherlands * MUS, abbreviation for Medically unexplained physical symptoms * MUS, abbreviation for the Memphis University School * MUS, abbreviation for the Movimiento Unión Soberanista * MUS, abbreviation for Multiple-use water supply system, a low-cost, equitable water supply systems * Mus, abbreviation for Musca, a southern constellation * mus, ISO-639 code for the Muscogee language * Mus., abbreviation used in music degrees such as B.Mus. and M.Mus. * MUs, or million units of energy, used in India for a gigawatt hour People * Anders Mus (fl. 1501–1535), Danish civil servant in Norway * Conny Mus (1950–2010), Dutch journalist, best known as a correspondent for ''RTL Nieuws'' in Israel and the Middle East * Gus Mus (born 1944), I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telomeres
A telomere (; ) is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Although there are different architectures, telomeres, in a broad sense, are a widespread genetic feature most commonly found in eukaryotes. In most, if not all species possessing them, they protect the terminal regions of chromosomal DNA from progressive degradation and ensure the integrity of linear chromosomes by preventing DNA repair systems from mistaking the very ends of the DNA strand for a double-strand break. Discovery In the early 1970s, Soviet theorist Alexei Olovnikov first recognized that chromosomes could not completely replicate their ends; this is known as the "end replication problem". Building on this, and accommodating Leonard Hayflick's idea of limited somatic cell division, Olovnikov suggested that DNA sequences are lost every time a cell replicates until the loss reaches a critical level, at which point cell division end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centromeres
The centromere links a pair of sister chromatids together during cell division. This constricted region of chromosome connects the sister chromatids, creating a short arm (p) and a long arm (q) on the chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore. The physical role of the centromere is to act as the site of assembly of the kinetochores – a highly complex multiprotein structure that is responsible for the actual events of chromosome segregation – i.e. binding microtubules and signaling to the cell cycle machinery when all chromosomes have adopted correct attachments to the spindle, so that it is safe for cell division to proceed to completion and for cells to enter anaphase. There are, broadly speaking, two types of centromeres. "Point centromeres" bind to specific proteins that recognize particular DNA sequences with high efficiency. Any piece of DNA with the point centromere DNA sequence on it will typically form a centromere if pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribosomal RNA
Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal DNA (rDNA) and then bound to ribosomal proteins to form SSU rRNA, small and LSU rRNA, large ribosome subunits. rRNA is the physical and mechanical factor of the ribosome that forces transfer RNA (tRNA) and messenger RNA (mRNA) to process and Translation (biology), translate the latter into proteins. Ribosomal RNA is the predominant form of RNA found in most cells; it makes up about 80% of cellular RNA despite never being translated into proteins itself. Ribosomes are composed of approximately 60% rRNA and 40% ribosomal proteins by mass. Structure Although the primary structure of rRNA sequences can vary across organisms, Base pair, base-pairing within these sequences commonly forms stem-loop configurations. The length and position of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleolar Organizing Regions
] Nucleolus organizer regions (NORs) are chromosome, chromosomal regions crucial for the formation of the nucleolus. In humans, the NORs are located on the short arms of the acrocentric chromosomes 13, 14, 15, 21 and 22, the genes RNR1, RNR2, RNR3, RNR4, and RNR5 respectively. These regions code for 5.8S, 18S, and 28S ribosomal RNA. The NORs are "sandwiched" between the repetitive, heterochromatic DNA sequences of the centromeres and telomeres. The exact sequence of these regions is not included in the human reference genome as of 2016 or the GRCh38.p10 released January 6, 2017. On 28 February 2019, GRCh38.p13 was released, which added the NOR sequences for the short arms of chromosomes 13, 14, 15, 21, and 22. However, it is known that NORs contain tandem copies of ribosomal DNA (rDNA) genes. Some sequences of flanking sequences proximal and distal to NORs have been reported. The NORs of a loris have been reported to be highly variable. There are also DNA sequences related t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Drift
Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. It can also cause initially rare alleles to become much more frequent and even fixed. When few copies of an allele exist, the effect of genetic drift is more notable, and when many copies exist, the effect is less notable. In the middle of the 20th century, vigorous debates occurred over the relative importance of natural selection versus neutral processes, including genetic drift. Ronald Fisher, who explained natural selection using Mendelian genetics, held the view that genetic drift plays at most a minor role in evolution, and this remained the dominant view for several decades. In 1968, population geneticist Motoo Kimura rekindled the debate with his neutral theory of molecular evolution, which claims that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Drive
Molecular drive is a term coined by Gabriel Dover in 1982 to describe evolutionary processes that change the genetic composition of a population through DNA turnover mechanisms. Molecular drive operates independently of natural selection and genetic drift. The best-known such process is the concerted evolution of genes present in many tandem copies, such as those for ribosomal RNAs or silk moth egg shell chorion proteins, in sexually reproducing species. The concept has been proposed to extend to the diversification of multigene families. The mechanisms involved include gene conversion, unequal crossing-over, transposition, slippage replication and RNA-mediated exchanges. Because mutations changing the sequence of one copy are less common than deletions, duplications and replacement of one copy by another, the copies gradually come to resemble each other much more than they would if they had been evolving independently. Concerted evolution can be unbiased, in which case eve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gabriel Dover
Gabriel A. Dover (13 December 1937 – 1 April 2018) was a British geneticist, best known for coining the term molecular drive in 1982 to describe a putative third evolutionary force operating distinctly from natural selection and genetic drift. Early life and education Dover was born in Manchester in 1937. Born to a Jewish family, his first degree was in Hebrew and Aramaic (first class) from the University of London in 1960. His adolescence included moving to Palestine in 1938–1942, and again for 5 years after the war, when he lived in Israel on a kibbutz. Described as "deeply politicised" and discomforted with the plight of the Palestinians he returned to the UK, and pursued a life in academia. He moved from a degree in Hebrew to the University of Leeds where he took a first in botany in 1969 followed by a PhD in plant genetics at Cambridge under Sir Ralph Riley. He subsequently took up academic positions (Lecturer in genetics at Cambridge, Head of Department at Leicester), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribosomal DNA
Ribosomal DNA (rDNA) is a DNA sequence that codes for ribosomal RNA. These sequences regulate transcription initiation and amplification, and contain both transcribed and non-transcribed spacer segments. In the human genome there are 5 chromosomes with nucleolus organizer regions: the acrocentric chromosomes 13 (RNR1), 14 ( RNR2), 15 ( RNR3), 21 (RNR4) and 22 (RNR5). The genes that are responsible for encoding the various sub-units of rRNA are located across multiple chromosomes in humans. But the genes that encode for rRNA are highly conserved across the domains, with only the copy numbers involved for the genes having varying numbers per species. In Bacteria, Archaea, and chloroplasts the rRNA is composed of different (smaller) units, the large (23S) ribosomal RNA, 16S ribosomal RNA and 5S rRNA. The 16S rRNA is widely used for phylogenetic studies. Eukaryotes The rRNA transcribed from the approximately 600 rDNA repeats forms the most abundant section of RNA found in cells ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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