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how can i get multiple fasta sequences using blast?

thank you for reading. i'm currently trying to making a database of NGS paired-end sequence data. i have 2 sequence data for each locus now(named R1 and R2.) i've already finshed getting sequence names whose sequences passed through the quality checks using grep command. however, i can not figure out how to get the
sequences by using just one file as a query which contains the sequence names at the same time. i'd appriciate it if you could tell me that kind of command. thank you.

gene

Not exactly sure what you are asking but you can use filterbyname.sh from BBMap suite to extract reads you need from a larger fastq file. Run the program on its own to look at in-line help on other options. The program should also work with fasta sequences.

You should not need to use blast+.

$ filterbyname.sh

Written by Brian Bushnell
Last modified September 1, 2016

Description:  Filters reads by name.

Usage:  filterbyname.sh in=<file> in2=<file2> out=<outfile> out2=<outfile2> names=<string,string,string> include=<t/f>

names=          A list of strings or files.  The files can have one name per line, or
                be a standard read file (fasta, fastq, or sam).

thank you for your prompt reply. i'm sorry for my unclear contexts. i have some marker sequences now and i want to extract sequences which contains the markers from both R1 and 2 sequences. anyway, i'll try that command. thank you.

This link might help:

https://ncbi.github.io/magicblast/cook/paired.html

For SRA accessions Magic-BLAST determines whether reads are paired and maps them appropriately.

For reads in FASTA and FASTQ files paired reads can either be in a single file, or two files.

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