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The Genom of Homo sapiens.pdf

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260 MARGULIES ET AL.Figure 4. General strategy for detecting MCSs. (A) <strong>The</strong> amount <strong>of</strong> sequence conservation (with the human reference sequence) is calculatedfor each overlapping 25-base window <strong>of</strong> a multispecies sequence alignment. (B) <strong>The</strong> contribution <strong>of</strong> each species’ sequenceto the conservation score is weighted based on the neutral substitution rate between that species and human (indicated are the calculatedsimilarities at neutral positions, with the neutral substitution rates being 1 minus these values); in this fashion, the ultimate contribution<strong>of</strong> an alignment to the resulting conservation score depends on the difference between the percent identity <strong>of</strong> that alignmentand the corresponding neutral rate for that species (as illustrated for cat and platypus). (C) In general, coding regions (yellow) havehigher conservation scores than noncoding regions (purple). A conservation score threshold (vertical arrow) is selected such that 5%<strong>of</strong> the total sequence resides within the detected MCSs (red); importantly, this results in virtually all coding sequence and a very smallamount <strong>of</strong> noncoding sequence falling within MCSs. For additional details, see Margulies et al. (2003).

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