Questions tagged [blast]

Basic Local Alignment Search Tool: algorithm that finds regions of similarity between a pair of sequences, can be used to query an unknown sequence against a database of known sequences.

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21 views

mpiblast alternatives?

I am looking for a sequence alignment software capable of pairwise alignment of a large number of protein sequences (10^7). I tried to go for mpiblast: https://wiki.canterbury.ac.nz/display/UCHPC/...
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1answer
380 views

Biopython - extracting query coverage from XML Blast output

I need to extract (or to calculate precisely) the query coverage from Blast output. I am using NCBIWWW.qblast to query Blast in XML format. Is it possible to know the query coverage parsing the XML ...
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How to use SRA Toolkit to blast SRA accessions?

I'm trying to look for a gene in a group of SRA files. Web BLAST can't cope with them, so I assume they're too large. I've tried tblastn_vdb from the SRA toolkit, as follows. It had previously worked ...
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1answer
27 views

how could i find uniprot ac in blast?

I have made a search in p-blast. I would like to search for the protein results in uniprot. how can I do it directly? I can go to GENBANK but i would like to go to UNIPROT. Thank you!!!
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1answer
60 views

Pseudocode for gapped BLAST seed extension

I am trying to understand in detail how does the gapped BLAST seed extension DP algorithm works. Despite searching for days now, I could not find anywhere a pseudocode that would allow implementing ...
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Difference in BLAST and eggNOG

Note: this question has also been asked on Biostars This is question regarding the tools rather than the concepts. I am a freshman at college and I am a working on an evolutionary biology of ...
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1answer
66 views

Find species from FASTA files

In a school project we got the task of finding the species from two FASTA files. We got some hints of what to look for, like it is a unicellular eukaryote and that we can use blast. We don't know if ...
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1answer
81 views

How low does an E-Value need to be for a gene to code for the same protein as query?

I'm looking at a bacterial genome and trying to find specific PEGs (Protein Encoding Genes) by BLAST searching. I'm taking the genes found with the lowest E-value in order to psiBLAST them to check it ...
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2answers
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Timeout when downloading the ncbi nr blast database

I am experiencing timeout problems when downloading the NCBI nr preformatted blast database using the update_blastdb script (version 504861). I run the script with the following paramters ...
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1answer
64 views

Translating a genome sequence into possible frames

I have a sequence below from MYC gene about which I need to translate the sequence in all possible frames AND identify (for each frame) which codons are actually used in MYC ...
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1answer
77 views

What kind of BLAST do I need to do to accomplish this task?

(I am a complete newbie to bioinformatics, so please bear with me!). I recently used BLAST to compare a 500 bp nucleotide sequence in S. cerevisiae to a bunch of other 500 bp nucleotide sequences in ...
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1answer
2k views

Can't install newest Blast from Conda

I have run into an odd situation, where Anaconda repo page clearly states that the newest version of Blast in Bioconda channel is 2.7.1, however the version Conda wants to install (command ...
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1answer
50 views

How to identify genes from a genome assembly of C. Elegans?

I have two full genome assemblies for C. Elegans samples collected from two different geographical areas that I found on WormBase. These are in fasta format. I want to go gene-by-gene and compare the ...
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33 views

How to read E-value annotation on NCBI BLAST?

i am a bit confused how to read the current E value annotation on NCBI BLAST results. I looked into the matter but could not find an factual answer . What i understood so far: E -values are the ...
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2answers
694 views

How is BLAST's nr database created?

Is there a paper or web page describing the procedure for creating the nr database used by NCBI's BLAST implementation? I presume it's some type of clustering, but I'm curious about how exactly ...
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1answer
198 views

How to do BLASTP for short sequences (<20 aa) effectively?

I am trying to find sequence homology between viral sequences and my protein of interest. I have the sequences of their epitopes which varies from 5 to 500 amino acids long. For shorter sequences, it ...
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Analyzing a blast result of NGS data

I am analyzing BLAST results from total RNA NGS, pair ends. This BLAST results was performed against the ssRNA virus database download from NCBI. I filtered those read data whose paired ends ...
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1answer
57 views

How to identify unknow bacterium species from whole genome genetic sequence

I am a Biochemist that is unfamiliar with bioinformatic tools and new to academia as a whole. I am currently using ILLUMINA PE data, which I trimmed (Trimmomatic), corrected (Rcorrector) and assembled ...
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What is the meaning of letter 'c' in tblastn results before genomic sequence position?

An example of a result. So far I have been unable to find the answer on my own. ">CP000000.0:c2005000-2006000 Escherichia coli strain XYZ chromosome ATG..."
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1answer
37 views

Does BLASTClust guarantee that proteins in different clusters are dissimilar?

I need to find dissimilar proteins. Looking through the PDB I found the weekly BLASTClust results of proteins that are 30% similar. However, I do not know if protein A in cluster 1 is guaranteed to be ...
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Genome assembly of SRR12196449 with SPAdes

I am trying to assemble the run SRR12196449 with SPAdes. The description of their project is: This project expected to standardize a method for amplification and ...
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2answers
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how can i search in p-blast against UNIPROT(not only swissprot)

i need to search for one protein against UNIPROT in BLAST for a selected organism. How can I do it? (SWSISSPROT+TREMBL) THANKS!!
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Please help me with my command!

I am looking for a command to count the total number of unique proteins in a file. For instance I wrote a command to BLAST XYZ proteins as query against the DLY proteins as a database to determine the ...
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2answers
63 views

BLASTn query coverage discrepancy

Using the BLASTn webtool with, Query Seq: CAATTGCGAAGCCACATTATT Subject Seq: CP031332.1 BLASTn returns a single hit to CP031332.1 with query coverage at 100%. However if one looks at the alignment, ...
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191 views

which NCBI tool is optimized to identify a species from a DNA fragment?

“The Iceman” was a man who lived 5300 years ago and whose body was recovered from an Alpine glacier in 1991. Some fungal material was recovered from his clothing and sequenced. Ice man : found as a ...
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1answer
71 views

NCBI blast for exact match of a short sequence

I'm trying to Blast for exact matches to the sequence: 'ATTGNNNNGCAAACCA' in the human transcriptome using NCBI Blast on its 'refseq_rna' database. However, when I do a basic query I get "No ...
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1answer
102 views

Plotting distance tree from blastn output

I'm trying to plot a simple distance tree of my blastn output with nj (like the tree view on NCBI). From what I understood, what I think I should do is extract all the hsps from each alignment re-...
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How to find possible viral subsequences in a Eukaryote genome?

I have an assembly of an algae and want to find if it has anything analogous to endogenous retroviruses' subsequences in its DNA. My guess is I should manually blastn all subsequences until I find (or ...
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82 views

Does NCBI's blast API block my IP?

I am trying to run a blatn command from both my laptop and within a google colab notebook. I am not sure why, but this command runs properly once and then, on the ...
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1answer
235 views

Is there any tool for fuzzy sequence matching?

Note: this question was also asked on biostars are you aware of any tool that is able to perform error-tolerant pattern-matching search on protein FASTA files? For example, I want to know, which ...
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Blast templates not found in PSI-TM Coffee

I'm trying to run psicoffe mode on Ubuntu 18.04, but it returns the error: 17633 -- WARNING: Impossible to find BLAST Templates Check that your blast server is properly installed [See documentation][...
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46 views

Software for taxonomic assignment?

I have a couple of hundred bacterial sequences of 2-30 genes of interest each, recovered from metagenomics. None of them encode rRNA. Normally I'd just BLAST the one gene I already know to be reliable ...
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2answers
743 views

how to have a blast xml file in a readable and understandable way

I got a blast xml file after a DNA sequence search. The XML file is not very readable. What is the way to make it more understandable? This blast contains about twenty matches. Here is the xml file
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1answer
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Blast results filters

I performed a blastn search of NGS data against ssRNA database download from Internet, with a expected value 10-4. The size of NGS data reads is of 125 bp. I have analyzed the blast results of the ...
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phmm blast hmmer

i have created a phmm in hmmer from a multiple alignment focused on E. coli produced in tcoffee from sequences taken from blast similar to my query sequence. I would like to ask how i can compare the ...
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1answer
78 views

Do you know a program/script to count how many sequences have mismatches on each position of my primers?

I'm working with primer analysis and design, and so far I've performing it in Excel but: a) I don't like Excel, b) I do it manually, c) I don't like Excel, d) it gets tedious when working with ...
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Finding orthologues using BLAST on the NCBI database

I'm an informatics student who has essentially zero knowledge of biology. I BLASTed my gene and have 1000s of results with very low E values. Where do I go from here if I want to find orthologues?
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BLAST, last step: Needleman-Wunsch + S-score

In my bioinformatics course we studied the BLAST agorithm. After finding the HSP's and joining the HSPs together that are close enough and in a correct diagonal trend, we perform a next step: namely a ...
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1answer
47 views

Standalone Blast+; Automating searches, Blastn formatting, interpretation

I am struggling with using NCBI's standalone blast, particularly the blastn feature. I have a large number of nucleotide sequences that I want to use blastn to ID. The goal is to retrieve information ...
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2answers
370 views

Transform traditional blast output to `--outfmt 6`

I have run a blastx of metagenomic databases (raw illumina reads) using the nr database. Unfortunately, I forgot to add the --outfmt 6 argument to the code and got ...
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BERT Language Model and Gene Sequences - How Do I Relate Clusters of Sequences?

I hope you'll indulge a question from a computer scientist with limited bioinformatics knowledge. I've been working with the Google tool for language modeling called BERT. It's generally regarded ...
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1answer
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Can you give me a detailed explanation about PrimeBlast?

I am trying to write a research paper on PRIMER-BLAST. I have read something about it on https://www.ncbi.nlm.nih.gov/pubmed/22708584/ but still, it is not enough. So can you please tell me more ...
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Primer-Blast Custom Database [error]

I'm using Primer-Blast to compare a PCR template against a custom database of reference sequences, using Primer-Blast's Custom database functionality. However whenever I try to upload a FASTA file as ...
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715 views

changing blast parameters using NCBIWWW module

I have found a blog post with a script that I would like to use for my current research project: link The script is incredibly fast and produces a smooth conservation plot. In the blog post, the ...
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1answer
51 views

how to generate structure file from blast results of an input sequence

I have tried to incorporate blast in my application using biopython.i could extract the blast results but now i want to extract the structure file corresponding matches. My code is : ...
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255 views

Cannot blast against specific NCBI databases

I am having issues with some prokaryote reference genome databases (exact names : ref_prok_rep_genomes.*), that I downloaded from the NCBI website : https://ftp.ncbi.nlm.nih.gov/blast/db/. Files in ...
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1answer
79 views

Possibility to save output blastn table in memory using biopython

Is there a possibility, using biopython to save output table of blastn in memory, not in file on hard drive, for process it using pandas for example and then delete it from memory? I mean, is there a ...
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1answer
904 views

Cannot blast database created with blastdb_aliastool: BLAST Database error: No alias or index file found

I want to merge/concatenate BLAST databases as suggested here. This is my example script that explains what I'm trying to achieve better than words can: ...
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216 views

What are the different kinds of bioluminescent genes?

I know of the common green glow gene but I forgot the name and I also know that some algae glow blue. There are so many types of bioluminesent organisms, so I am wondering what species have which ...
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2answers
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Is there a "definitive" database for Mobile Genetic Elements?

This isn't quite my speciality, but I've been tasked with finding any evidence of Mobile Genetic Elements (like transposable elements, retrotransposons, bacteriophages, etc.) within some WGS samples. ...