| FS | factor of safety; Fanconi syndrome; Felty syndrome; fibromyalgia syndrome; field stimulation; Fisher... |
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| fra(X) | fragile X chromosome, fragile X syndrome |
| FMR | fragile site mental retardation [syndrome]; Friend-Moloney-Rauscher [antigen] |
| FRAXE | X-linked mental retardation-fragile site [syndrome] |
| AFRAX | autism-fragile X [syndrome] |
| Site 1 | site |
|---|---|
| FS | Fragile Sites |
| Fra(X) | Fragile X |
| FMR1 | Fragile X Mental Retardation gene 1 |
| FMR-1 | Fragile X Mental Retardation-1 |
| fragile site | Places on chromosomes that tend to break more often than other places. These places also tend to be where chromosomal translocations (a type of chromosomal mutation) occur. (09 Oct 1997) |
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| chromosome fragile sites | Heritable sensitive regions of chromosomes which show up in vitro as non-staining bands. They are associated with chromosome breakage and other aberrations, and, when located on sex chromosomes, they produce phenotypic abnormalities. No abnormal phenotype has been definitely identified with autosomal fragile sites, but some rare autosomal recessive disorders may be due to homozygosity for fragile sites. Fragile sites are designated by the letters "fra" followed by the designation for the specific chromosome and locus. (12 Dec 1998) |
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| syndrome, fragile x | The most common heritable form of mental retardation. Fragile x syndrome is due to mutation (changes) at the fragile x site and so perforce is x-linked (carried on the x chromosome). Although it is usually more severe in males than females, the syndrome is due to a dynamic mutation (a trinucleotide repeat) that can change in length and hence in severity from generation to generation, from person to person, and even within a given person. The fragile x syndrome is also known as the martin-bell syndrome in honor of their discovery of it in 1943. (12 Dec 1998) |
| fragile x chromosome | X chromosome with a fragile site associated with a frequent form of mental retardation. The fragile X chromosome was first sighted by Herbert A. Lubs in 1969. The fragile X is also called FRAXA (the second A signifies it was the first FRAgile site found on the X chromosome). It is due a trinucleotide repeat (a recurring motif of 3 bases) in the DNA at that spot. (12 Dec 1998) |
| fragile X syndrome | <syndrome> most frequent cause of mental retardation. There is an expanded trinucleotide repeat CGG in the fra(X) gene. There is usually a constricted section on the long arm of the X chromosome. After puberty these patients often exhibit large prominent ears, long narrow face, coarse facial features and macroorchidism. Mental retardation in males is characteristic although the manifestations of the syndrome are highly variable. A preponderance of males are affected but it also affects 30% of carrier females and about 20% of obligate carrier males are not affected. The complexity in the inheritance pattern comes from the fact that these obligate carrier males (transmitting males) pass on the mutation to all their daughters (unaffected). most of the sons of carrier females with the mutation are mentally retarded but of their daughters, only 1/3 are retarded while 1/3 are borderline retarded and 1/3 are normal. Penetrance of the disease is variable within families and among siblings. Another unique characteristic of this syndrome, which is referred to as the Sherman Paradox is the fact that the risk of a family member being abnormal when gene-positive depends on the position of the proband in the pedigree. Sons of phenotypically normal but transmitting males have no risk of being mentally affected, but grandsons and great-grandsons of the transmitting a male have a much higher risk of mental retardation (40% and 50%, respectively). On the other hand, if the carrier female expresses the mental handicap her sons have a 50% risk of mental retardation. The classical method of confirming diagnosis is culture of lymphocytes in a folate-free medium (or supplemented with trimethoprim, methotrexate or FUdR) and microscopic detection of the fragile site (Xq27.3). Expression is seen in less than 50% of the cells of affected individuals but the test is not applicable to carrier detection as there is a high false negative rate (60%). The fragile-X gene (FMR-1), which contains tandemly repeated trinucleotide sequences (CGG repeats) on its 5' end, can be detected with PCR or Southern blot techniques. Normal controls show 6-50 CGG repeats, whereas mutation in affected males or heterozygous females can contain as many as 1,000 CGG repeat units. The test is indicated for individuals with compatible mental retardation, developmental delays or autism, or for those that have a family history of the syndrome. It is also indicated for prenatal detection in offspring of carrier females. Inheritance: sex-linked. Incidence: 1 in 1200 males and 1 in 2500 females. (17 Dec 1997) |
| acceptor site | The ribosomal binding site for the aminoacyl-tRNA during protein synthesis. (05 Mar 2000) |
| acceptor splicing site | Boundary between the right end of an intron and the left end of the adjacent exon. Synonym: acceptor splicing site. (05 Mar 2000) |
| active site | <chemistry> A specific region of an enzyme where a substrate binds and catalysis takes place (binding site). (06 May 1997) |
| allosteric site | A specific site on a multi-subunit enzyme or other protein that is not the substrate binding site, but that when reversibly bound by an effector, induces a conformational change in the protein, altering its catalytic or binding properties. (12 Dec 1998) |
| amidation site | <molecular biology> A C terminus consensus sequence, required for C terminus amidation of peptides. Consensus is glycine, followed by 2 basic amino acids (arg or lys). (18 Nov 1997) |
| antibody combining site | <immunology> In immune network theory, an idiotope, an antigenic site of an antibody that is responsible for that antibody binding to an antigenic determinant (epitope). Also used of the site on a ligand molecule to which a cell surface receptor binds. (18 Nov 1997) |
| antigen-binding site | <immunology> In immune network theory, an idiotope, an antigenic site of an antibody that is responsible for that antibody binding to an antigenic determinant (epitope). Also used of the site on a ligand molecule to which a cell surface receptor binds. (18 Nov 1997) |
| antigen-combining site | See: paratope. (05 Mar 2000) |
| apurinic site | <molecular biology> Sites in DNA from which purines have been lost by cleavage of the deoxy ribose N glycosidic linkage. (18 Nov 1997) |
| apyrimidinic site | <molecular biology> A site on DNA where a base is missing, in this case a pyrimidine (either cytosine or thymine), but the phosphodiester backbone is still intact. Compare: apurinic site. (09 Oct 1997) |
| ATT site | <molecular biology> A site on the chromosome of the bacteria E. Coli where the lambda bacteriophage can insert its genome (all of its DNA) so that it can lie dormant and have its DNA reproduced whenever the bacterium reproduces for as long as the bacterium remains healthy (that is, so that it becomes lysogenic). (09 Oct 1997) |
| fragile site |
Chromosomal anomaly that appears as a region of decondensed or partially broken mitotic chromosomes under specific karyotyping conditions. The FRAXA and FRAXE fragile sites contain expanded CGG repeats that are methylated, affecting the expression of the FMR1 and FMR2 genes, respectively.
Ãâó: www.nature.com/nrg/journal/v2/n9/glossary/nrg0901_...
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| fragile site |
A chromosomal region that has a tendency to break.
Ãâó: helios.bto.ed.ac.uk/bto/glossary/ef.htm
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| fragile site |
A small break or a constriction of a chromosome that can be visualised after special treatment of the chromosomes. In individuals affected with fragile X syndrome, a fragile site can often be seen on their X chromosome.
Ãâó: www.agsa-geneticsupport.org.au/glossary.html
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