DNA analysis in amelogenesis imperfecta

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A gene was cloned form the proximal short arm of the human Y chromosome. Later, a homologous gene was cloned from the distal short arm of the X chromosome. Both genes were sequenced for about 2.8kb and 3 exons were identified in both of them. The exones of both genes showed about 93% sequence homology. It was later identified that they were amelogenin gene on X and amelogenin-like gene on Y.Studies of families with amelogenesis imperfecta revealed that in a large family with sex-linked amelogenesis imperfecta, all the affected members showed a 5kb deletion of the amelogenin gene involving all the 3 exones. The results definitely showed that sex-linked amelogenesis imperfecta was caused by the abnormality of the amelogenin gene. None of autosomal recessive or autosomal dominant families showed abnormality of the amelogenin gene.The amelogenin-like gene on Yp had an about 180bp deletion within an intron. A set of primers was designated which enabled a simultaneous detection of both X and Y sequences by PCR.The technique much improved the reliability of the sec determination by PCR.