signal ratio for each possible transition or transversion. The labelling for polymorphisms is the allele in the reference strain (C57BL/6J) followed by the allele in the test strain. E.g. A/C indicates that the reference strain has an A at the relevant position, and the test strain has a C. Since the probes are all designed to be complementary to the C57BL/6J reference, this means that there is an A-T base pair for C57BL/6J and a C-T pair for the test strain. Error bars represent the standard error.