diff --git a/examples/bdd/generators/gen_drs.py b/examples/bdd/generators/gen_drs.py
index dd0edf4..87a8f1f 100755
--- a/examples/bdd/generators/gen_drs.py
+++ b/examples/bdd/generators/gen_drs.py
@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 
 import sys
+import itertools
 
 
 class SingleReaction:
@@ -19,15 +20,19 @@ class SingleReaction:
         return "{" + ", ".join(self.products) + "}"
 
     def __str__(self):
-        return "{" + f"{self.get_reactants()}, {self.get_inhibitors()} -> {self.get_products()}" + "};"
+        return (
+            "{"
+            + f"{self.get_reactants()}, {self.get_inhibitors()} -> {self.get_products()}"
+            + "};"
+        )
 
 
 class Reactions:
     def __init__(self):
-        self.reactions = set()
+        self.reactions = []
 
     def add(self, reaction):
-        self.reactions.add(reaction)
+        self.reactions.append(reaction)
 
     def __str__(self):
         ret = ""
@@ -54,10 +59,19 @@ class DRSGenerator:
         rcts.add(SingleReaction(["GF"], ["h", f"RTK{i}"], ["RTK"]))
         rcts.add(SingleReaction(["RTK"], [f"ENi:1_{i}"], [f"EN:1_{i}"]))
         for j in range(1, self.x):
-            rcts.add(SingleReaction([f"EN:{j}_{i}"], [f"ENi:{j+1}_{i}"], [f"EN:{j+1}_{i}"]))
+            rcts.add(
+                SingleReaction([f"EN:{j}_{i}"], [f"ENi:{j+1}_{i}"], [f"EN:{j+1}_{i}"])
+            )
+
+        indices = list(range(1, self.y + 1))
+        for comb in itertools.combinations(indices, self.z):
+            reactants = []
+            for i in comb:
+                reactants.append(f"EN:{self.x}_{i}")
+            rcts.add(SingleReaction(reactants, ["h"], ["TF"]))
 
     def generate(self):
-        for i in range(1, self.y):
+        for i in range(1, self.y + 1):
             self.generate_reactions_for_component(i)
 
         for proc, reactions in self.reactions.items():