Which is the following is not inherited as X-linked recessive:March 2005, September 2012, March 2013

Ans. C: Cystic fibrosisX-linked diseases usually occur in males.Males have only one X chromosome.A single recessive gene on that X chromosome will cause the disease.The Y chromosome is the other half of the XY gene pair in the male.However, the Y chromosome doesn't contain most of the genes of the X chromosome.It therefore doesn't protect the male.This is seen in diseases such as hemophilia and Duchenne muscular dystrophy.Autosomal dominant:Examples of this type of disorder are Huntington's disease, Neurofibromatosis 1, Marfan Syndrome, Hereditary nonpolyposis colorectal cancer, and Hereditary multiple exostoses, which is a highly penetrant autosomal dominant disorder.Autosomal recessiveExamples of this type of disorder are cystic fibrosis, sickle-cell disease, Tay-Sachs disease, Niemann-Pick disease, spinal muscular atrophy etc.3X-linked dominantX-linked hvpophosphatemic rickets, Rett syndrome, Incontinentia Pigmenti type 2 and Aicardi SyndromeX-linked recessiveX-linked recessive conditions include the serious diseases Hemophilia A, Duchenne muscular dystrophy, G-6-PD deficiency and Lesch-Nyhan syndrome as well as common and less serious conditions such as male pattern baldness and red-green color blindness.Y-linked disordersExamples are Male Infeility and hyperichosis pinnae.