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Topic Review
Chromosomal instability in Fanconi anemia
Fanconi anemia (FA), a chromosomal instability syndrome, is caused by inherited pathogenic variants in any of 22 FANC genes, which cooperate in the FA/BRCA pathway. This pathway regulates the repair of DNA interstrand crosslinks (ICLs) through homologous recombination. In FA proper repair of ICLs is impaired and accumulation of toxic DNA double strand breaks occurs. To repair this type of DNA damage, FA cells activate alternative error-prone DNA repair pathways, which may lead to the formation of gross structural chromosome aberrations of which radial figures are the hallmark of FA, and their segregation during cell division are the origin of subsequent aberrations such as translocations, dicentrics and acentric fragments. The deficiency in DNA repair has pleiotropic consequences in the phenotype of patients with FA, including developmental alterations, bone marrow failure and an extreme risk to develop cancer.
  • 1.7K
  • 15 Jan 2021
Topic Review
Maximum Genetic Diversity
Maximum Genetic Diversity (MGD) is a scientific hypothesis relating to molecular evolution, which is the study of how and why populations of organisms experience genetic changes over time. MGD starts with the observation that some regions of the genome are more likely to preserve mutations into the next generation than others. This difference in the observed rate of mutation means some regions of the genome appear to mutate faster than others, and is theorized to relate to balancing the preservation of vital information relating to a species' function against its ability to mutate and adapt to new environmental niches. According to MGD, these regions of the genome eventually drift into two rough categories: faster-mutating sections tuned to respond quickly to environmental pressures and allow adaptive radiation, as well as slower-mutating sections involved in an organism's most fundamental instructions. Because MGD asserts that only slow-mutating genes accurately reflect shared evolutionary history, relationships between species can alternatively be calculated by their "maximum genetic diversity," which is determined by measuring the frequency of mutations in specific corresponding regions of orthologous genes instead of using raw overall genetic similarity. Using calculations based on mutations in these slow-mutating genes provides a chart of genetic ancestry that lines up with the fossil record – measurements based on raw genetic similarity yield results that clash with the fossil record. Also due to this grouping into fast and slow, MGD hypothesizes that over time complex organisms become genetically fragile and less tolerant to mutation as their MGD decreases, since an increasing proportion of their genome will have become slow-mutating over time. MGD asserts that this is because increased organismal and social complexity means more of the genome is needed to preserve the expanding instructional manual necessary for complex behavior and function, and so more of an organism's genome must become slow-mutating as the organism increases in complexity, since being slow-mutating preserves and protects those vital instructions. MGD seeks to reconcile the inconsistencies observed around the neutral theory of molecular evolution, whose "original lines of evidence... are now falsified" according to a paper published in Oxford's Molecular Biology and Evolution in 2018. One example of this is that supposedly consistent and neutral mutation rates from proteins across a wide range of species were demonstrably not neutral nor consistent. Another study published in Nature in December 2019 noted that "defining the evolutionary time scales according to the molecular clock is intrinsically biased, especially for proteins of complex organisms." Although a number of other arguments have been proposed against the neutral theory in recent years, there is not a yet a consensus that the neutral theory is entirely falsified and counter-arguments against the role of selection do exist. Furthermore, beyond the fact that MGD is still relatively unknown, it also contradicts the current paradigm in molecular evolution, since the neutral theory's fundamental premises are still nearly ubiquitously utilized in genetic analysis and admixture studies. Additionally, some of the phenomena explained by MGD could theoretically be accounted for by other processes such as gene conversion or concerted evolution. Lastly, even if the neutral theory is disproved, it does not necessarily validate MGD, as alternative theories have been proposed that also incorporate the effects of selection on the genome. And so MGD will have to be more rigorously tested against any alternative theories before becoming widely adopted. However, to date MGD has not been contradicted in peer-reviewed literature, and its assumptions and framework have been confirmed when it comes to examining the ratio of brain-specific proteins in a range of mammals, for classifying and timing the evolutionary genetic structure of a wide range of organisms ranging from yeast to primates, by evaluating the genetic fitness of yeast which become more genetically fragile as they become more fit, by a genetic model that seeks to more accurately model not only the location of mutations but the rate at which they occur, and by the observation that vital slow-mutating genes are more protected by "transcriptional scanning" in mammalian testes than fast-evolving genes involved with responding quickly to environmental challenges.
  • 1.7K
  • 25 Nov 2022
Topic Review
Cat Body-type Mutation
Cats, like all living organisms, occasionally have mutations that affect their body type. Sometimes, these cat body-type mutations are striking enough that humans select for and perpetuate them. This is not always in the best interests of the cat, as many of these mutations are harmful; some are even lethal in their homozygous form. This article gives a selection of cat body type mutant alleles and the associated mutations with a brief description.
  • 1.6K
  • 29 Sep 2022
Topic Review
Structural Variation
Mutations in DNA can be limited to one or a few nucleotides, or encompass larger deletions, insertions, duplications, inversions and translocations that span long stretches of DNA or even full chromosomes. These so-called structural variations (SVs) can alter the gene copy number, modify open reading frames, change regulatory sequences or chromatin structure and thus result in major phenotypic changes. 
  • 1.6K
  • 10 May 2021
Topic Review
Hybrid Rye Breeding and Production
Hybrid rye breeding leads to considerably higher grain yield and a higher revenue to the farmer. The basis of hybrid seed production is the CMS-inducing Pampa (P) cytoplasm derived from an Argentinean landrace and restorer-to-fertility (Rf) genes. Breeding is based on inbred line development and intensive testing for line per se performance and general combining ability (GCA). The finally selected inbred lines are used to compose a topcross hybrid with two genetically different seed parent lines (A-P, B-N) and a restorer synthetic composed of two S2 lines (SynRf). European restorer sources show low-to-moderate pollen-fertility levels. This results in higher susceptibility to ergot (Claviceps purpurea) because rye pollen and ergot spores are in strong competition for the unfertilized stigma. Rf genes from non-adapted Iranian primitive rye and old Argentinean cultivars proved to be most effective. The major Rf gene in these sources was localized on chromosome 4RL, which is also a hotspot of restoration in other Triticeae. Commercial hybrids with these Rf genes showed a similar low ergot infection when compared with population cultivars. The great future challenges of climate change, such as increased drought stress tolerance, improved lodging tolerance, as well as the increasing need for resistant varieties can effectively only be met by hybrid breeding.
  • 1.6K
  • 06 May 2022
Topic Review
DNA Mismatch Repair Gene Variants
DNA mismatch repair system (MMR) is an integral part of DNA damage response pathway (DDR), responsible for maintenance of genomic integrity. MMR preferably corrects frameshift mutations in microsatellites and mismatched nucleotides generated during DNA replication.
  • 1.6K
  • 26 Oct 2020
Topic Review
Peripartum Cardiomyopathy
Peripartum cardiomyopathy (PPCM) is a condition in which heart failure and left ventricular systolic dysfunction occur in the last month of pregnancy or within months following delivery.
  • 1.6K
  • 26 Jan 2021
Topic Review
Chromosome 19
Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 19, one copy inherited from each parent, form one of the pairs.
  • 1.6K
  • 24 Dec 2020
Topic Review
MEGDEL Syndrome
MEGDEL syndrome is an inherited disorder that affects multiple body systems. It is named for several of its features: 3-methylglutaconic aciduria (MEG), deafness (D), encephalopathy (E), and Leigh-like disease (L).
  • 1.6K
  • 23 Dec 2020
Topic Review
FBLN5 Gene
Fibulin 5: The FBLN5 gene provides instructions for making a protein called fibulin-5. 
  • 1.6K
  • 25 Dec 2020
Topic Review
Y Chromosome Evolution and Functional Specialization
The Y chromosome is one of the sex chromosomes found in males of animals of different taxa, including insects and mammals. Among all chromosomes, the Y chromosome is characterized by a unique chromatin landscape undergoing dynamic evolutionary change. Being entirely heterochromatic, the Y chromosome as a rule preserves few functional genes, but is enriched in tandem repeats and transposons. Due to difficulties in the assembly of the highly repetitive Y chromosome sequence, deep analyses of Y chromosome evolution, structure, and functions are limited to a few species, one of them being Drosophila melanogaster. Here researchers survey comparative evolutionary history of the fly and human Y chromosomes, and functions of Y-linked piRNA clusters ensuring sex-specific piRNA silencing. 
  • 1.6K
  • 09 May 2022
Topic Review
LINE1 Retrotransposons
LINE-1 (L1) is a class of autonomous mobile genetic elements that form somatic mosaicisms in various tissues of the organism. The activity of L1 retrotransposons is strictly controlled by many factors in somatic and germ cells at all stages of ontogenesis. Alteration of L1 activity was noted in a number of diseases: in neuropsychiatric and autoimmune diseases, as well as in various forms of cancer.
  • 1.6K
  • 20 Oct 2021
Topic Review
LYST Gene
Lysosomal trafficking regulator
  • 1.5K
  • 23 Dec 2020
Topic Review
Cytoplasmic Actin Mutations
Cytoplasmic actins are abundant molecules in non-muscle cells, including white blood cells. Two forms exist which are referred to as beta- or gamma-cytoplasmic actin encoded by ACTB and ACTG1, respectively. They form the building blocks of the dynamic actin polymers of the cytoskeleton that are involved in migration and motility processes of cells. Whereas mutations in cytoplasmic actins have been discovered in congenital diseases, their prevalence in cancer types has not been studied in detail. We show that within hematological cancer cytoplasmic actin mutations occur with higher frequency in two specific subtypes. Beta-actin mutations occur mainly in the subtype diffuse large B-cell lymphoma or DLBCL whereas gamma-actin mutations occur mainly in multiple myeloma. Mapping these mutations on the three dimensional structure reveals they map to regions of actin that are important in actin polymer formation and, for gamma-actin also for myosin interaction. Given their occurrence in these functionally important regions, their role as potential driver mutations or in disease progression merits further investigation.
  • 1.5K
  • 28 Oct 2020
Topic Review
Limb Development
The function of retinoic acid (RA) during limb development is still debated, as loss and gain of function studies led to opposite conclusions. With regard to limb initiation, genetic studies demonstrated that activation of FGF10 signaling is required for the emergence of limb buds from the trunk, with Tbx5 and RA signaling acting upstream in the forelimb field, whereas Tbx4 and Pitx1 act upstream in the hindlimb field. Early studies in chick embryos suggested that RA as well as Meis1 and Meis2 (Meis1/2) are required for subsequent proximodistal patterning of both forelimbs and hindlimbs, with RA diffusing from the trunk, functioning to activate Meis1/2 specifically in the proximal limb bud mesoderm. However, genetic loss of RA signaling does not result in loss of limb Meis1/2 expression and limb patterning is normal, although Meis1/2 expression is reduced in trunk somitic mesoderm. More recent studies demonstrated that global genetic loss of Meis1/2 results in a somite defect and failure of limb bud initiation. Other new studies reported that conditional genetic loss of Meis1/2 in the limb results in proximodistal patterning defects, and distal FGF8 signaling represses Meis1/2 to constrain its expression to the proximal limb.
  • 1.5K
  • 19 Jan 2021
Topic Review
Gene Disease Database
In bioinformatics, a Gene Disease Database is a systematized collection of data, typically structured to model aspects of reality, in a way to comprehend the underlying mechanisms of complex diseases, by understanding multiple composite interactions between phenotype-genotype relationships and gene-disease mechanisms. Gene Disease Databases integrate human gene-disease associations from various expert curated databases and text mining derived associations including Mendelian, complex and environmental diseases.
  • 1.5K
  • 21 Nov 2022
Topic Review
Ohdo Syndrome, Say-Barber-Biesecker-Young-Simpson Variant
The Say-Barber-Biesecker-Young-Simpson (SBBYS) variant of Ohdo syndrome is a rare condition characterized by genital abnormalities in males, missing or underdeveloped kneecaps (patellae), intellectual disability, distinctive facial features, and abnormalities affecting other parts of the body.
  • 1.5K
  • 24 Dec 2020
Topic Review
Papaya Flavour Profiling
A major challenge to the papaya industry is inconsistency in fruit quality and, in particular, flavour, which is a complex trait that comprises taste perception in the mouth (sweetness, acidity, or bitterness) and aroma produced by several volatile compounds. Current commercial varieties vary greatly in their taste, likely due to historical prioritised selection for fruit appearance as well as large environmental effects. Therefore, it is important to better understand the genetic and biochemical mechanisms and biosynthesis pathways underpinning preferable flavour in order to select and breed for better tasting new commercial papaya varieties. As an initial step, objectively measurable standards of the compound profiles that provide papaya’s taste and aroma, together with ‘mouth feel’, are required. This review presents an overview of the approaches to characterise the flavour profiles of papaya through sugar component determination, volatile compound detection, sensory panel testing, as well as genomics-based studies to identify the papaya flavour. 
  • 1.5K
  • 27 Sep 2021
Topic Review
The Genetic Architecture of SLD
Specific Learning Disorder (SLD) is a multifactorial, neurodevelopmental disorder which may involve persistent difficulties in reading (dyslexia), written expression and/or mathematics. Dyslexia is characterized by difficulties with speed and accuracy of word reading, deficient decoding abilities, and poor spelling. Several studies from different, but complementary, scientific disciplines have investigated possible causal/risk factors for SLD. Biological, neurological, hereditary, cognitive, linguistic-phonological, developmental and environmental factors have been incriminated. Despite worldwide agreement that SLD is highly heritable, its exact biological basis remains elusive.
  • 1.5K
  • 09 Jul 2021
Topic Review
Transposable Elements
Transposable elements (TEs) are mobile DNA sequences that can jump from one genomic locus to another and that have colonized the genomes of all living organisms. While TE mobilization is an important source of genomic innovations that greatly contribute to the host species evolution, it is also a major threat to genome integrity that can lead to pathologies.
  • 1.5K
  • 26 May 2022
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