Fluorescent in situ hybridization to answer a clinical question. This 
shows chromosomes of a black man with tyrosinase-negative albinism. 
Since only one mutation in the tyrosinase gene was identified and the 
man was also mentally retarded, the question arose whether the other 
gene was lost through a submicroscopic deletion. In situ hybridization 
of a biotin- labeled cosmid clone containing the human tyrosinase gene 
revealed a signal (large yellow spots) on both chromosomes 11, where 
the tyrosinase genes reside, thus ruling out a deletion and forcing the 
conclusion that he is homozygous for the rare mutation. 
Cells and cosmid provided by Richard Spritz. Experiment done by 
Chih-Lin Hsieh, HHMl Associate at Stanford. Imaging on a Phoibos 
confocal laser scanning microscope. 
From Spritz, R.A., Strunk, K.M., Hsieh, C. L., Sekhon, G.S., and 
Francke, U. 1991. Am J Hum Genet 48:318-324. ® 1991 by the Ameri- 
can Society of Human Genetics. 
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