二代测序的局限性

长度150bp以下的reads理论上在基因组的很多位置都是没办法unique定位的

比如：

CACTACAATTATGTGTGGCAACGCATGTGTCGGCATTATGGCTGTCGCATGGGGAATTGGCTTTCTCCATTCGGTGAGCCAGTTGGCGTTTGCCGTGCACTTACTCTTCTGTGGTCCCAATGAGGTCGATAGTTTTTATTGTGACCTTCC

https://genome.ucsc.edu/cgi-bin/hgBlat

 ACTIONS      QUERY           SCORE START  END QSIZE IDENTITY CHRO STRAND  START    END      SPAN
---------------------------------------------------------------------------------------------------
browser details YourSeq          148     1   150   150  99.4%     1   +      69465     69614    150
browser details YourSeq          146     1   150   150  98.7%    15   -  101922536 101922685    150
browser details YourSeq          146     1   150   150  98.7%    19   +     111053    111202    150
browser details YourSeq           36   107   150   150  91.0%    14   +   19936168  19936211     44
browser details YourSeq           20    99   118   150 100.0%     4   -  107986813 107986832     20