The off-target effect, in which DNA cleavage was conducted outside the targeted region, is a major problem which limits the applications of CRISPR/Cas9 genome editing system. CRISPR Off-target Predictor (CROP) is standalone program developed to address this problem by predicting off-target propensity of guide RNAs and thereby allowing the user to select the optimum guides. The approach used by CROP involves generating substitution, deletion and insertion combinations which are then mapped into the reference genome. Based on these mapped variants, scoring and alignment are conducted and then reported as a table comprising the off-target propensity of all guide RNAs from a given gene sequence. The Python script for this program is freely available from: https://github.com/vaprilyanto/crop.

脱靶效应，即DNA切割在目标区域之外进行，是限制CRISPR/Cas9基因组编辑系统应用的主要问题。 CRISPR 脱靶预测器 (CROP) 是为解决这一问题而开发的独立程序，通过预测向导 RNA 的脱靶倾向，从而允许用户选择最佳向导。 CROP 使用的方法涉及生成替换、删除和插入组合，然后将其映射到参考基因组中。基于这些映射的变体，进行评分和比对，然后以表格形式报告，其中包含给定基因序列的所有向导RNA的脱靶倾向。该程序的 Python 脚本可从以下位置免费获取：https://github.com/vaprilyanto/crop.