Twist Bioscience Human Exome panel
A platform for human whole exome sequencing (WES) using target enrichment and library preparation for next generation sequencing.
At NGI, we offer whole exome sequencing including library preparation and enrichment using the Twist Human Comprehensive Exome Kit from Twist Bioscience.
Sample requirements
- Sample type: high-quality DNA
- Amount of sample: minimum 200 ng
- Volume: 25-50 µL
- Amount of material needed for preparing one library: 50 ng
How to evaluate the sample quality
We check your samples upon arrival, however we still require our users to do their own QC steps before sending samples.
Checking the concentration
Please use fluorometric measurements (e.g. Qubit, Quant-it), not absorbance measurements (Nanodrop, spectrophotometer).
Checking the quality and purity
The DNA should be in water or EB buffer, of high quality, and ideally have an OD260/280 of 1.8-2.
The DNA is enzymatically fragmented during library preparation. Buffers with EDTA may inhibit the fragmentation. Please use non-EDTA based buffers or low EDTA-buffers.
If your samples are below the required thresholds, please get in touch.
What we do with your samples
Once your samples arrive at NGI, we start by performing a reception control step in which we make sure the samples meet our requirements.
If the samples fail this quality control step, we will contact you to discuss possible options. Should you choose to proceed with samples not fulfilling the criteria it will be at your own risk, NGI will only make one attempt at library preparation and if the library preparation does not work you will be charged to the for the library preparation regardless.
If the samples pass reception control, the samples will be queued for library preparation.
Library preparation
The protocol for library preparation involves DNA fragmentation and ligation of Illumina adapters with sample-specific barcodes. After sample and library preparation, a hybridization-based target enrichment step is performed using probes that contain specific sequences that are designed to bind complementary to the exome DNA sequences
Library QC and sequencing
We evaluate the concentration of the libraries using qPCR and look at the fragment size distribution of the library molecules using TapeStation or FragmentAnalyzer. Once the libraries have passed this QC step, they are normalised, pooled, and queued for sequencing.
The sequencing will be carried out following the setup stated in the agreement.
Expected results
In general, we have been successfully generating libraries that provide enough good quality reads for sequencing of genomic DNA. However, the sequencing results from each library prep will depend on the characteristics of the sample:
- The yield of the library preparation could be insufficient when the input is below our input criteria or if the DNA is degraded.
- When the library concentration is too low, generating an even pooling is more difficult, so you can expect uneven reads yields.
Last Updated: 1st September 2021