第一次聽到這個概念，很懵，只知道是FLT3基因的內部段串聯重復，因為之前是做遺傳病相關，也接觸過段串聯重復序列，

后來經過文獻閱讀，發現完全不是一回事情。

遺傳病中的短串聯重復序列：（摘自百度百科）

短串聯重復序列 (STR, short tandem repeats) STR: 短串聯重復序列（short tandem repeats，STR）也稱微衛星 DNA（microsatellite DNA）,

通常是基因組中由1~6個堿基單元組成的一段DNA重復序列，由于核心單位重復數目在個體間呈高度變異性并且數量豐富，構成了STR基因座的遺傳多態性。

一般認為人類基因組平均每15 kb就存在一個STR基因座。人類基因組DNA中平均每6～10kb就有一個STR位點，

其多態性成為法醫物證檢驗個人識別和親子鑒定的豐富來源。

不同人體基因組衛星DNA重復單位的數目是可變的，因此，形成了極其復雜的等位基因片段長度多態性。

白血病中FLT3/ITD串聯重復序列：

Informatics of insertion detection. A: The FLT3 ITD is an insertion of duplicated and nonduplicated sequence that occurs between exons 13 and

14. These insertions (shown in gray) range in size from 15 to w300 bp. B: Standard methods for fifinding insertions, including the Genome Analysis Toolkit
(GATK), SAMtools, and Dindel, apply probabilistic models to make insertion calls based on data obtained during the initial read mapping and alignment
process. Because of the diffificulty associated with aligning short reads, only small insertion events (generally <15% of the total read length) can be identifified
by this approach (aligned reads are shown in green; unaligned reads, in purple). Such reads generally have suffificient homology in the regions flflanking the
insertion to permit accurate alignment. Large insertions (>16 bp), including the FLT3 ITD, are too long to be detected by this method. C: Using a paired-end
approach, software such as Pindel and de novo alignment can reliably detect larger insertions, including the FLT3 ITD. In this approach, mate-pairs are
identifified in which one end is mapped, but the other is not. The unmapped mates are then assembled to form contigs with partial homology to the reference
sequence, using a pattern-growth algorithm (Pindel) or de novo assembly with a custom script (unpublished data) executing Phrap assembly software. This
method allows for the detection of much larger insertions.

參考文獻：

Spencer D H , Abel H J , Lockwood C M , et al. Detection of FLT3 Internal Tandem Duplication in Targeted, Short-Read-Length, Next-Generation Sequencing Data[J]. The Journal of molecular diagnostics: JMD, 2012, 15(1).

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