Improvements And Extensions To The Blast Algorithms

已修改程序tblaetry，以便其替换 可以通过成分缩放或条件缩放来修改矩阵。 成分矩阵调整 因为查询是一个DNA序列 这是概念上是翻译成六个框架，至少有五个 这通常是不正确的，矩阵修改需要 定义用于计算序列的序列窗口 混合物. 我们已经构造了一种方法来定义这样的窗口 这会产生很好的经验结果。 我们的研究显示 任一类型的替换矩阵修改产生统计 比基线计划的要精确得多， 而检索准确性仅伴随有较小的降低。 今年的进一步工作集中在扩展PSI-BLAST上， 它能够利用相关序列位置的信息 从多重比对推断。

The program tblastn has been modified so that its substitution matrix may be modified by either compositional scaling or conditional compositional matrix adjustment. Because the query is a DNA sequence that is conceptually is translated in six frames, at least five of which are usually incorrect, matrix modification requires the definition of a sequence window from which to calculate sequence composition. We have constructed a way to define such a window that yields good empirical results. Our studies have shown that either type of substitution matrix modification yields statistics that are much more accurate than those of the baseline program, with only a minor attendant decrease in retrieval accuracy. Further work this year has focussed on extending PSI-BLAST so that it is able to use information on correlated sequence positions deduced from multiple alignments.