Large but still submicroscopic i

Large but still submicroscopic i - . For instance, some...

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Large but still submicroscopic i.e. less than 1Mb Almost all cases of X linked ichthyosis are brought about by total deletion of the gene STS , coding for steroid sulphatase. This is caused by a mutation which seems to be recurrent. The STS gene is flanked by two copies of a repetitve element. It is thought that sometimes in meiosis these two copies, on the same chromatid, align and recombine leading to excision of the DNA between them as in the figure below. Sometimes deletions can cover more than one gene. When this occurs we have an example of a contiguous gene syndrome
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Unformatted text preview: . For instance, some patients with Tuberous sclerosis also suffer from polycystic kidney disease. The two loci TSC2 and PKD are adjacent on chromosome 16 and can be simultaneously deleted. Cytogenetic Some deletions become so large that they are visible on well stretched metaphase chromosomes. When enough of the genome is deleted to be visible in this way, the symptoms are usually very severe because a large number (probably more than a hundred) genes will have been lost. Contiguous gene syndromes will become likely....
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This note was uploaded on 11/22/2011 for the course CHEMISTRY CHM1025 taught by Professor Laurachoudry during the Fall '10 term at Broward College.

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