as last descriptor. nGU+(nGU−) MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGUbGBdaqhaaWcbaGaem4raCKaemyvaufabaGaey4kaScaaOGaeiikaGIaemOBa42aa0baaSqaaiabdEeahjabdwfavbqaaiabgkHiTaaakiabcMcaPaaa@37F9@ denotes the number of GU base pairs in the consensus secondary structure of the reading direction of the input alignment (reverse complement of the input alignment), and nall+ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGUbGBdaqhaaWcbaGaemyyaeMaemiBaWMaemiBaWgabaGaey4kaScaaaaa@332D@ and nall− MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGUbGBdaqhaaWcbaGaemyyaeMaemiBaWMaemiBaWgabaGaeyOeI0caaaaa@3338@ are the numbers of all base pairs in the consensus structure of the corresponding reading direction. Fig. 2 shows that alignments in the reading direction of a tRNA can not as easy be separated from the reverse complementary alignments by evaluating only Δmeanmfe, Δmeanz, Δconsmfe and Δsci as it is the case for alignments containing U70 snoRNAs. The majority of tRNAs have around 0–5% GU base pairs in their consensus secondary structure. (The percentage of GU pairs is roughly λGU/2.) In contrast, the majority of U70 snoRNAs have 10% to 20% GU base pairs in their consensus structure. λGU allows the SVM to find suitable classification values depending on the fraction of GU base pairs. Therefore, U70 snoRNAs as well as tRNAs are classified correctly with high accuracies (U70: 1.0, tRNA: 0.94).