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blast中word-size参数是什么意思?

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发表于 2013-4-25 19:13:55 | 显示全部楼层 |阅读模式
下面是我在NCBI官网上找到的解释,不过看不太懂,希望前辈能通俗的解释下这个参数的意思什么的。
PS。不是要原文翻译,是要解释下
blast is a heuristic that works by finding word-matches between the query and database sequences. One may think of this process as finding "hot-spots" that BLAST can then use to initiate extensions that might eventually lead to full-blown alignments. For nucleotide-nucleotide searches (i.e., "blastn") an exact match of the entire word is required before an extension is initiated, so that one normally regulates the sensitivity and speed of the search by increasing or decreasing the word-size. For other BLAST searches non-exact word matches are taken into account based upon the similarity between words. The amount of similarity can be varied so one normally uses just the word-sizes 2 and 3 for these searches.
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