Introduction to Genetic Analysis 619

Introduction to Genetic Analysis 619 - base pairs for such...

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Unformatted text preview: base pairs for such polymorphisms. However, when one is found, we do not know which of the six base pairs at the recognition site is polymorphic. If we use enzymes that recognize four-base se- quences (four cutters), there is a recognition site every 4 4 256 base pairs, so a panel of eight different en- zymes can sample about once every 256/8 32 base pairs along the DNA sequence. In addition to single base-pair changes that destroy restriction-enzyme recog- nition sites, there are insertions and deletions of stretches of DNA that occur along the DNA strand be- tween the locations of restriction sites, and these will also cause restriction fragment lengths to vary. A variety of different restriction-enzyme studies has been performed for different regions of the X chromo- some and the two large autosomes of Drosophila melanogaster. These have found between 0.1 and 1.0 percent heterozygosity per nucleotide site, with an aver- age of 0.4 percent. The result of one such study on the xanthine dehydrogenase gene in...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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