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fragile X syndrome

A chromosomal disease, often associated with mental retardation, in which the tip of the long arm of the X chromosome can separate from the rest of the genetic material. This is the most common of the X-linked mental retardation syndromes. Most males and 30% of females with this syndrome are mentally retarded. Males also develop greatly enlarged testicles (macro-orchidism), enlarged ears, and a prominent jaw.


(fră-jĭl′ĭ-tăs) [L.] Fragility.


(fră-jĭl′ĭt-ē) Brittleness; having the property of being readily broken, injured, or damaged.

bone f., bony f. Any structural defect of bone that increases the likelihood of fracture. Common diseases that increase bone fragility include osteoporosis and osteomalacia.

capillary f. A breakdown of capillaries with hemorrhage into almost any site but most noticeably in the skin.

f. of red blood cells The tendency of red blood cells to rupture. This is determined by subjecting the cells to different concentrations of saline in laboratory tests.

 If red blood cells are placed in distilled water, they swell rapidly and burst because they normally are suspended in a solution of much greater osmotic pressure. This phenomenon is called hemolysis. If they are suspended in a solution of normal saline, the cells retain their normal shape and do not burst. If they are placed in successively weaker solutions of saline, a point is reached at which some of the cells burst and liberate their hemoglobin within a given length of time. Finally, at a given dilution, all the cells have burst within the allotted time, which is usually 2 hr. Normal blood cells begin to hemolyze in about 0.44% saline solution, and complete hemolysis occurs in about 0.35% solution.


(frăg′mĕnt) A part broken off a larger entity.

Fab f. Area on an immunoglobulin (antibody) to which antigens bind. The enzyme papain splits antibodies into three fragments, two Fab fragments, each of which is antigen-specific, and an Fc or crystallizable fragment, which is involved in secondary antibody activities such as activating complement.

immunoglobulin f. The portion of the IgG molecule that contains an antibody-combining site. Specific fragments are obtained by treating the molecule with the enzyme papain under specified conditions. The resultant fragments are designated “F(zz) Fragment,” where zz represents the specific fragment. SYN: immunoglobulin isotype.

fragment antigen binding

ABBR: Fab. Area on an immunoglobulin (antibody) to which antigens bind.


(frăg″mĕn-tā′shŭn) [L. fragmentum, detached part] Breaking up into pieces.

sleep f. Arousals and awakenings that disrupt the normal stages and architecture of sleep. These events, which occur commonly in patients who have sleep apnea or ...

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