ALLR (Average Log Likelihood Ratio) at each position along the aligned DNA sequences, comparing different distributions. For the red (upper) curve the two compared distributions are the same. The curve lies above zero. Around TSS, the ALLR increases due to a higher similarity with the background profile (5000 random genes). The blue (middle) curve again represents the ALLR values comparing the "1 tissue" expression group with itself, but now the G+C content of one distribution was artificially increased to test the effect caused by GC isochores. The black curve (bottom) compares the "1 tissue" with the "all tissues" expression groups. It represents two effects: one of the GC isochores (where it coincides with the blue curve), and one of the CpG island effect (where it deviates from the blue curve around TSS).