# STAR-FUSION: "BLAST+-blastn of the reference fasta sequence with itself"- cannot generate a last-matching gene pairs file

**URL:** <https://help.galaxyproject.org/t/star-fusion-blast-blastn-of-the-reference-fasta-sequence-with-itself-cannot-generate-a-last-matching-gene-pairs-file/7915>\
**Category:** Uncategorized\
**Tags:** blast\
**Created:** [April 24, 2022, 3:52am UTC](https://help.galaxyproject.org/t/star-fusion-blast-blastn-of-the-reference-fasta-sequence-with-itself-cannot-generate-a-last-matching-gene-pairs-file/7915 "2022-04-24T03:52:34Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Kwok\_MJL](https://sea2.discourse-cdn.com/flex020/user_avatar/help.galaxyproject.org/kwok_mjl/32/3322_2.png) [@Kwok\_MJL](https://help.galaxyproject.org/u/Kwok_MJL)\
**Post date:** [April 24, 2022, 3:52am UTC](https://help.galaxyproject.org/t/star-fusion-blast-blastn-of-the-reference-fasta-sequence-with-itself-cannot-generate-a-last-matching-gene-pairs-file/7915/1 "2022-04-24T03:52:34Z")

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Hi all,

I am using Star-fusion. To generate a last-matching gene pairs file, I download “GRCh37\_gencode\_v19\_CTAT\_lib\_Mar012021.source.tar.gz” from [Index of /Trinity/CTAT\_RESOURCE\_LIB](https://data.broadinstitute.org/Trinity/CTAT_RESOURCE_LIB/)  
I run it in the NCBI BLAST+ blastn ([https://usegalaxy.org/](https://usegalaxy.org/)) as:

Nucleotide query sequence(s): GRCh37\_gencode\_v19\_CTAT\_lib\_Mar012021.source.tar.gz  
Subject database/sequences: GRCh37\_gencode\_v19\_CTAT\_lib\_Mar012021.source.tar.gz  
Type of BLAST: blastn - Traditional BLASTN requiring an exact match of 11, for somewhat similar sequences  
Output format: Tabular (standard 12 columns)

However, i cannot generate a last-matching gene pairs file. Does anyone know what goes wrong? Many thanks.