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Dynamic Mutation
In genetics, a dynamic mutation is an unstable heritable element where the probability of expression of a mutant phenotype is a function of the number of copies of the mutation. That is, the Reproduction, replication product (offspring, progeny) of a dynamic mutation has a different likelihood of mutation than its predecessor. These mutations, typically short sequences repeated many times, give rise to numerous known diseases, including the trinucleotide repeat disorders. Robert I. Richards and Grant R. Sutherland called these phenomena, in the framework of dynamical genetics, dynamic mutations. Triplet expansion is caused by slippage during DNA replication. Due to the repetitive nature of the DNA sequence in these regions , 'loop out' structures may form during DNA replication while maintaining complementary base pairing between the parent strand and daughter strand being synthesized. If the loop out structure is formed from sequence on the daughter strand this will result in an i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetics
Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar working in the 19th century in Brno, was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene. Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded to study the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell, the organism (e.g. dominance), and within the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. There are two forms of reproduction: asexual and sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms. The cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically similar or identical copy of itself. The evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sexual reproduction is that only 50% of organisms reproduce and organisms only pass on 50% of their genes.John Maynard Smith ''The Evolution of Sex'' 1978. Sexual reproduction typically requires the sexual interaction of two specializ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Offspring
In biology, offspring are the young creation of living organisms, produced either by a single organism or, in the case of sexual reproduction, two organisms. Collective offspring may be known as a brood or progeny in a more general way. This can refer to a set of simultaneous offspring, such as the chicks hatched from one clutch of eggs, or to all the offspring, as with the honeybee. Human offspring ( descendants) are referred to as children (without reference to age, thus one can refer to a parent's " minor children" or " adult children" or " infant children" or " teenage children" depending on their age); male children are sons and female children are daughters (see kinship). Offspring can occur after mating or after artificial insemination. Offspring contains many parts and properties that are precise and accurate in what they consist of, and what they define. As the offspring of a new species, also known as a child or f1 generation, consist of genes of the father and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trinucleotide Repeat Disorders
Trinucleotide repeat disorders, also known as microsatellite expansion diseases, are a set of over 50 genetic disorders caused by trinucleotide repeat expansion, a kind of mutation in which repeats of three nucleotides ( trinucleotide repeats) increase in copy numbers until they cross a threshold above which they become unstable. Depending on its location, the unstable trinucleotide repeat may cause defects in a protein encoded by a gene; change the regulation of gene expression; produce a toxic RNA, or lead to chromosome instability. In general, the larger the expansion the faster the onset of disease, and the more severe the disease becomes. Trinucleotide repeats are a subset of a larger class of unstable microsatellite repeats that occur throughout all genomes. The first trinucleotide repeat disease to be identified was fragile X syndrome, which has since been mapped to the long arm of the X chromosome. Patients carry from 230 to 4000 CGG repeats in the gene that causes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamical Genetics
Dynamical genetics concerns the study and the interpretation of those phenomena in which physiological enzymatic protein complexes alter the DNA, in a more or less sophisticated way. The study of such mechanisms is important firstly since they promote useful functions, as for example the immune system recombination (on individual scale) and the crossing-over (on evolutionary scale); secondly since they may sometimes become harmful because of some malfunctioning, causing for example neurodegenerative disorders. Typical examples of dynamical genetics subjects are: * dynamic mutations, term introduced by Robert I. Richards and Grant R. Sutherland to indicate mutations caused by other mutations; this phenomenon often involves the variable number tandem repeats,{{cite journal , last1=Fonzo , first1=VD , last2=Bersani , first2=E , last3=Aluffi-Pentini , first3=F , last4=Parisi , first4=V , title=DNA quadruplexes and dynamical genetics. , journal=Medical Hypotheses , date=July 2001 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Replication
In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential. DNA is made up of a double helix of two complementary strands. The double helix describes the appearance of a double-stranded DNA which is thus composed of two linear strands that run opposite to each other and twist together to form. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. As a result of semi-conservative rep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anticipation (genetics)
In genetics, anticipation is a phenomenon whereby as a genetic disorder is passed on to the next generation, the symptoms of the genetic disorder become apparent at an earlier age with each generation. In most cases, an increase in the severity of symptoms is also noted. Anticipation is common in trinucleotide repeat disorders, such as Huntington's disease and myotonic dystrophy, where a dynamic mutation in DNA occurs. All of these diseases have neurological symptoms. Prior to the understanding of the genetic mechanism for anticipation, it was debated whether anticipation was a true biological phenomenon or whether the earlier age of diagnosis was related to heightened awareness of disease symptoms within a family. Trinucleotide repeats and expansion Trinucleotide repeats are apparent in a number of loci in the human genome. They have been found in introns, exons and 5' or 3' UTR's. They consist of a pattern of three nucleotides (e.g. CGG) which is repeated a number of times. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Sherman Paradox
The Sherman paradox was a term used to describe the anomalous pattern of inheritance found in fragile X syndrome. The phenomenon is also referred to as anticipation or dynamic mutation. Background The paradox was named in the late 1980s after American geneticist Stephanie Sherman, who studied the inheritance patterns of people with fragile X syndrome. Sherman observed that the effects of fragile X syndrome seemed to occur more frequently with each passing generation. This observation became known as the Sherman paradox. The paradox was ultimately explained by insights into the mutation process that gives rise to the syndrome. Sherman theorized that the gene responsible for fragile X syndrome becomes mutated through a two-step process. The first mutation, called the 'premutation', doesn't cause any clinical symptoms. A second mutation was required to convert the 'premutation' into a 'full mutation' capable of causing the clinical symptoms associated with fragile X syndrome. Additi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fragile X Syndrome
Fragile X syndrome (FXS) is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may include a long and narrow face, large ears, flexible fingers, and large testicles. About a third of those affected have features of autism such as problems with social interactions and delayed speech. Hyperactivity is common, and seizures occur in about 10%. Males are usually more affected than females. This disorder and finding of Fragile X syndrome has an X-linked dominant inheritance. It is typically caused by an expansion of the CGG triplet repeat within the ''FMR1'' (fragile X messenger ribonucleoprotein 1) gene on the X chromosome. This results in silencing ( methylation) of this part of the gene and a deficiency of the resultant protein (FMRP), which is required for the normal development of connections between neurons. Diagno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Huntington's Disease
Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an unsteady gait often follow. It is also a basal ganglia disease causing a hyperkinetic movement disorder known as chorea. As the disease advances, uncoordinated, involuntary body movements of chorea become more apparent. Physical abilities gradually worsen until coordinated movement becomes difficult and the person is unable to talk. Mental abilities generally decline into dementia. The specific symptoms vary somewhat between people. Symptoms usually begin between 30 and 50 years of age but can start at any age. The disease may develop earlier in each successive generation. About eight percent of cases start before the age of 20 years, and are known as ''juvenile HD'', which typically present with the slow movement symptoms of Parkinson's d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myotonic Dystrophy
Myotonic dystrophy (DM) is a type of muscular dystrophy, a group of genetic disorders that cause progressive muscle loss and weakness. In DM, muscles are often unable to relax after contraction. Other manifestations may include cataracts, intellectual disability and heart conduction problems. In men, there may be early balding and an inability to have children. While myotonic dystrophy can occur at any age, onset is typically in the 20s and 30s. Myotonic dystrophy is caused by a genetic mutation in one of two genes. Mutation of the '' DMPK'' gene causes myotonic dystrophy type 1 (DM1). Mutation of '' CNBP'' gene causes type 2 (DM2). DM is typically inherited from a person's parents, following an autosomal dominant inheritance pattern, and it generally worsens with each generation. A type of DM1 may be apparent at birth. DM2 is generally milder. Diagnosis is confirmed by genetic testing. There is no cure. Treatments may include braces or wheelchairs, pacemakers and non ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinal And Bulbar Muscular Atrophy
Spinal and bulbar muscular atrophy (SBMA), popularly known as Kennedy's disease, is a debilitating neurodegenerative disorder resulting in muscle cramps and progressive weakness due to degeneration of motor neurons in the brainstem and spinal cord and muscle wasting. The condition is associated with mutation of the androgen receptor (''AR'') gene and is inherited in an X-linked recessive manner. As with many genetic disorders, no cure is known, although research continues. Because of its endocrine manifestations related to the impairment of the ''AR'' gene, patients with SBMA develop partial symptoms of androgen insensitivity syndrome (AIS) in addition to neuromuscular degeneration. SBMA is related to other neurodegenerative diseases caused by similar mutations, such as Huntington's disease. The prevalence of SBMA has been estimated at 2.6:100,000 males. Signs and symptoms Individuals with SBMA have muscle cramps and progressive weakness due to degeneration of motor neurons in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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