GBS services are only for OSU internal projects. Contact the core lab if you have questions about this policy.
Why do a titration?
If you are using a new organism/enzyme combination, is important to determine the ratio of barcoded adapters to use in a GBS experiment. If the ratio is not correct, then much of the data output represents the primer-dimer and data for the intended library is significantly reduced. This ratio can be different for each organism-restriction enzyme combination.
Determining the ratio is done empirically by running a titration experiment. The titration experiment uses eight (8) concentrations of adapters with genomic DNA of the species of interest.
Two micrograms (2ug) of high quality genomic DNA (GBS quality) is the total amount needed for the titration experiment.
Eight libraries are prepared using a titration of adapters and assayed on a BioAnalyzer High Sensitivity (HS) DNA chip. The concentration of adapters which gives a good library with the smallest adapter peak is used for a GBS experiment.
Once the ratio of adapters is determined for a given species and restriction enzyme, that should be used for any GBS experiments with that organism-restriction enzyme combination.
Currently, we are using adapters designed for the ApeKI restriction enzyme.
If you are using an organism/enzyme combination that we have prepared libraries for previously, it is not necessary to do a titration. If any adapter peak is seen in the final library, we can complete a second magnetic-bead based cleanup to remove it before sequencing.