Lidstrom:Sequencing with GeneWiz

When Sequencing Fails

• There are several ways it can fail & you can see the GeneWiz help for causes/solutions below. You can also watch this GeneWiz webinar.
  • Non-specific
    • multiple are present on your DNA, or you accidentally have a mixture of DNA templates
    • hairpin present
  • Poor quality
    • high background: there is a clear sequence but there is also a background sequence.
      • remnants of chromosomal DNA
      • primer degradation: recall that your sequencing is dependent on length. So if you have one population of primers that is 20 bp and one that is 18 bp, they will give two separate signals.
    • top heavy: beginning sequence is strong; peaks may even be cut off. As it gets longer, the signal dies off. This is due to improper primer:template ratio; your primer may be "used up".
  • No priming: lots of "N"s in sequencing result
    • too much, too little, or no DNA
    • no primer or sub-optimal primer concentration
    • primer site not complementary
    • carry-over inhibitors in the reaction such as phenol, ethanol, EDTA, or salts
  • Early termination
    • hairpin present, repetitive sequence, or high GC content can terminate the rxn sequencing. Note: they have several "difficult sequencing" protocols that can be used; select them in the form.
  • bubble in capillary
    • can appear as a smear. You won't know when this happens, but customer support may be able to tell.
  • dye blobs
    • [image:dye_blob_GeneWiz.png|thumb]

• You can submit 2 samples per order for a free repeat, but they must be on the same templates you submitted.
• You can resequence as many as you like for 1/2 price and you have the choice to use new preps. This allows you to use a fresh miniprep or primer batch. If you want to submit fresh samples for 1/2 price, you may want to contact customer service and get approval. Once I put in a new order and note which are free repeats, and their respective order number in the "Notes" section of the form and they told me that was ok, but I got mixed messages about this. Janet 2/22/12
  • If you need to sequence another 1/2 price rxn, you should probably chat with customer service and they will put a note on the account. They usually tell you to put the name of who you chatted with on the form, too.
• Whether or not your repeat will be successful depends on several variables such as:
  • the concentration and quality of the sample -- if a "no priming" or "poor quality" samples is "no priming" or "poor quality" after you sequence again, the quality and quantity might be too bad to work the 2nd time.
  • you also may have a GC-rich region, hairpin or general difficult template that is causing binding issues, a problem with the binding site, a problem with the primer, etc.