blast比对是基因与基因之间进行比较，基因组序列比对没有意义。

1.可以用全基因组的方法，就是MCScanX分析的方法；

2.blast方法，串联重复与大片段复制定义如下：

Gene duplications are considered to be one of the primary driving forces in the evolution of genomes and genetic systems [22]. Duplicated genes provide raw material for the generation of new genes, which, in turn, facilitate the generation of new functions. Segmental duplication, tandem duplication, and transposition events, such as retroposition and replicative transposition [23], are considered to represent three principal evolutionary patterns. Of these patterns, segmental and tandem duplications have been suggested to represent two of the main causes of gene family expansion in plants [24]. Segmental duplications multiple genes through polyploidy followed by chromosome rearrangements [25]. It occurs most frequently in plants because most plants are diploidized polyploids and retain numerous duplicated chromosomal blocks within their genomes [24]. Tandem duplications were characterized as multiple members of one family occurring within the same intergenic region or in neighboring intergenic regions [26]. In this study, we defined tandem duplicated genes as adjacent homologous genes on a single chromosome, with no more than one intervening gene. For this analysis, we focused on segmental and tandem duplication events. To gain a greater insight about the expansion pattern of soybean expansin genes in this huge gene family, we identified tandem duplicated clusters based on the gene locus, and searched the Plant Genome Duplication Database [27] to locate segmentally duplicated pairs.

参考文献：

3.blast方法，串联重复与大片段复制判断方法如下：

https://link.springer.com/article/10.1007/s00425-016-2575-6 

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