An RNA molecule comprising a sensor part and a trigger part, wherein the trigger part is an mRNA coding for a protein and the sensor part comprises 2 stem loops divided in the following regions in order from 5' to 3': T (T1,T2), A, B, C (C1,C2), D (D1,D2), E, F (F1,F2) and G, wherein - region T1 is unpaired; - T2 forms a stem with B where A is the loop region; - C can be paired or unpaired; - D forms a stem with F, where E is the loop region; - F2 must contain an RBS; - stem loop D1 basepairs with F2 and D2 with F1; - G contains an ATG and a linker and is immediately followed by the trigger part; - further with the following structural limitations: a) T has a length of >= 30 nucleotides; b) T has the same number of nucleotides as B; c) D1 has the same number of nucleotides as F2 and D2 has the same number of nucleotides as F1: d) RBS in F1 is at least 3 nucleotides away from its start; e) (B + C1) has the same number of nucleotides as (D + E); f) D2 + E has the same number of nucleotides as T; g) C1 has the same number of nucleotides as D1; h) RBS in F2 must be at least 3 nucleotides away from F2 3' end; further wherein in the absence of a target RNA, the RBS in region F2 is sequestered in the DEF stem loop and thus, translation of the trigger is not possible; further wherein in the presence of a target RNA, the sensor part hybridizes the target RNA and a conformational change is produced, in which region T is sequestered by target RNA, B and C1 form a stem loop with D and E, where C2 is the loop region, F and G are partially or totally unpaired and thus the RBS in F2 is not sequestered and translation of the trigger is possible; and wherein RBS do not form stems with regions that also hybridize to the target RNA or form a stem with regions that hybridize with the regions which hybridize the target RNA. - region T1 is unpaired; - T2 forms a stem with B where A is the loop region; - C can be paired or unpaired; - D forms a stem with F, where E is the loop region; - F2 must contain an RBS; - stem loop D1 basepairs with F2 and D2 with F1; - G contains an ATG and a linker and is immediately followed by the trigger part; - further with the following structural limitations: a) T has a length of >= 30 nucleotides; b) T has the same number of nucleotides as B; c) D1 has the same number of nucleotides as F2 and D2 has the same number of nucleotides as F1: d) RBS in F1 is at least 3 nucleotides away from its start; e) (B + C1) has the same number of nucleotides as (D + E); f) D2 + E has the same number of nucleotides as T; g) C1 has the same number of nucleotides as D1; h) RBS in F2 must be at least 3 nucleotides away from F2 3' end; further wherein in the absence of a target RNA, the RBS in region F2 is sequestered in the DEF stem loop and thus, translation of the trigger is not possible; further wherein in the presence of a target RNA, the sensor part hybridizes the target RNA and a conformational change is produced, in which region T is sequestered by target RNA, B and C1 form a stem loop with D and E, where C2 is the loop region, F and G are partially or totally unpaired and thus the RBS in F2 is not sequestered and translation of the trigger is possible; and wherein RBS do not form stems with regions that also hybridize to the target RNA or form a stem with regions that hybridize with the regions which hybridize the target RNA. a) T has a length of >= 30 nucleotides; b) T has the same number of nucleotides as B; c) D1 has the same number of nucleotides as F2 and D2 has the same number of nucleotides as F1: d) RBS in F1 is at least 3 nucleotides away from its start; e) (B + C1) has the same number of nucleotides as (D + E); f) D2 + E has the same number of nucleotides as T; g) C1 has the same number of nucleotides as D1; h) RBS in F2 must be at least 3 nucleotides away from F2 3' end; further wherein in the absence of a target RNA, the RBS in region F2 is sequestered in the DEF stem loop and thus, translation of the trigger is not possible; further wherein in the presence of a target RNA, the sensor part hybridizes the target RNA and a conformational change is produced, in which region T is sequestered by target RNA, B and C1 form a stem loop with D and E, where C2 is the loop region, F and G are partially or totally unpaired and thus the RBS in F2 is not sequestered and translation of the trigger is possible; and wherein RBS do not form stems with regions that also hybridize to the target RNA or form a stem with regions that hybridize with the regions which hybridize the target RNA.