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the pattern of inheritance that may result from a mutant gene on an X chromosome.
x-link·ed in·he·rit·ance(lingk in-her'i-tăns)
Pattern of inheritance that may result from a mutant gene on an X chromosome.
The acquisition of traits, characteristics and disorders from parents to their children by transmission of genetic information. Genes come in pairs: one originating from the father, the other from the mother. If an individual presents only the hereditary characteristics determined by one gene of the pair on an autosomal chromosome, that gene is called dominant. Conditions caused by such genes are said to show autosomal dominant inheritance. For instance, for a rare autosomal dominant disease, if one parent is affected, then on average about 50% of their children will also be affected, irrespective of the children's sex. Examples: Marfan's syndrome, congenital stationary night blindness, neurofibromatosis 1 and 2, von Hippel-Lindau disease. If the individual does not present the hereditary characteristics unless both genes in a pair are of the same type, then the gene is called recessive. Conditions caused by such genes are said to show autosomal recessive inheritance. For a rare autosomal recessive disease, if a child is affected, then on average about 25% of their siblings will also be affected, irrespective of their sex. Examples: Laurence-Moon-Biedl syndrome, Tay-Sachs disease, oculocutaneous albinism, galactokinase deficiency.Thirdly, inheritance may be controlled by genes on one of the sex chromosomes, most often the X chromosome. A recessive mutation on the single X chromosome carried by a male will cause a disease, whereas in the female, a recessive X chromosome mutation would have to be carried on both of her X chromosomes. Therefore in X-linked recessive inheritance (sex-linked recessive inheritance) males are affected more often than females. Examples: colour blindness, ocular albinism, choroideremia. A fourth type of inheritance considered in ophthalmic practice is mitochondrial (maternal) inheritance in which the inheritance of a trait encoded in the mitochondrial DNA is transmitted through the female line (mother to son or mother to daughter). Examples: Leber's hereditary optic atrophy; Kearns-Sayre syndrome. See acquired; chromosome; defective colour vision; gene; hereditary.
|Table I5 Divisions of the infrared spectrum|
|IR-A (near)||780-1400 nm|
|IR-B (middle)||1400-3000 nm|
|IR-C (far)||3000-1 000 000 nm|