Unconfigured Ad

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • lran2008
    Member
    • Apr 2013
    • 35

    blast result against rfam database

    Hi All,

    I am blasting my miRNA-seq fasta file against rFam data base. Here is the command line I used:
    blastn -query TOTAL_mapped_reads.fa -task megablast -db Rfam.fasta -out mapped_vs_rfam.txt -outfmt "6 qseqid sseqid qlen evalue pident nident mismatch qcovs qcovhsp"

    Then I want to retrive those reads which match tRNAs in rFam.
    There are many hits in the output (see the attached picture).

    But when I pick the first read which is shown to be 100% match with rRNA in rfam by searching it in rfam website, there is no hit.
    >62-796337
    TCCCATATGGTCTAGCGGTTAGGATTCCTGGTT

    Briefly, according to my blast result against rfam database, there is a match, but when I search the my sequence in online rfam website, there is no hit. So what is the problem?
    Attached Files
  • rhinoceros
    Senior Member
    • Apr 2013
    • 372

    #2
    Based on blastn (at ncbi) your sequence is not a tRNA. The 'best' hit is "PREDICTED: Dasypus novemcinctus WW domain-binding protein 4-like (LOC101430251), transcript variant 2, mRNA".

    Perhaps consider a more conservative evalue cutoff? Also, how did you create your Rfam db? "-db Rfam.fasta" looks rather wrong to me but maybe you just named it oddly...
    savetherhino.org

    Comment

    • lran2008
      Member
      • Apr 2013
      • 35

      #3
      Originally posted by rhinoceros View Post
      Based on blastn (at ncbi) your sequence is not a tRNA. The 'best' hit is "PREDICTED: Dasypus novemcinctus WW domain-binding protein 4-like (LOC101430251), transcript variant 2, mRNA".

      Perhaps consider a more conservative evalue cutoff? Also, how did you create your Rfam db? "-db Rfam.fasta" looks rather wrong to me but maybe you just named it oddly...
      I indeed named it oddly. Anyway, it produced results, but seems to be unreliable... The e value for 62-796337 is 1e-10 in the attached picture. So what's your suggestion for the e value cutoff?

      Comment

      Latest Articles

      Collapse

      • SEQadmin2
        Advanced Sequencing Platforms Tackle Neuroscience’s Toughest Genomics Problems
        by SEQadmin2



        Genomics studies in neuroscience face a special challenge due to the brain’s complexity and scarcity of samples. Mapping changes in cell type and state using conventional next-generation sequencing methods remains challenging. Advances in technologies like single-cell sequencing, spatial transcriptomics, and long-read sequencing have opened the door to deeper studies of the brain and diseases like Alzheimer’s, amyotrophic lateral sclerosis (ALS), and schizophrenia.
        ...
        07-09-2026, 11:10 AM
      • SEQadmin2
        Cancer Drug Resistance: The Lingering Barrier to Rising Survival
        by SEQadmin2



        Cancer survival rates have significantly increased in the last few decades in the United States, reaching a combined 70% 5-year survival rate by 2021. Behind this number, there are years of research to find new therapies, drug targets, and early detection methods. But there is one core challenge that keeps slowing down these advances, and it’s about drug resistance.

        There is no single reason why many patients don’t respond to treatment as expected. Cancer is...
        07-08-2026, 05:17 AM
      • GATTACAT
        Reply to Nine Things a Sample Prep Scientist Thinks About Before Sequencing
        by GATTACAT
        Love this - good data definitely starts from good input, and poor input can only give relatively poor data. I particularly like the mention of Nanodrop/absorbance based methods for quantification. It's such a toss up if you'll get an accurate reading or what amounts to a randomly generated number, and a lot of library/sequencing related issues can be traced back to poor quant.
        07-01-2026, 11:43 AM

      ad_right_rmr

      Collapse

      News

      Collapse

      Topics Statistics Last Post
      Started by SEQadmin2, 07-09-2026, 10:04 AM
      0 responses
      11 views
      0 reactions
      Last Post SEQadmin2  
      Started by SEQadmin2, 07-08-2026, 10:08 AM
      0 responses
      9 views
      0 reactions
      Last Post SEQadmin2  
      Started by SEQadmin2, 07-07-2026, 11:05 AM
      0 responses
      17 views
      0 reactions
      Last Post SEQadmin2  
      Started by SEQadmin2, 07-02-2026, 11:08 AM
      0 responses
      31 views
      0 reactions
      Last Post SEQadmin2  
      Working...