diff --git a/src/entity_object.ts b/src/entity_object.ts
index ff5ab25..b2b67aa 100644
--- a/src/entity_object.ts
+++ b/src/entity_object.ts
@@ -5,15 +5,13 @@ export default class Entity implements BioLinkEntityObject {
   private _description: string;
   private _parent: string;
   private _children: string[];
-  private _ancestors: Entity[];
-  private _descendants: Entity[];
   private _id_prefixes: string[];
   private _name: string;
 
   constructor(name: string, info: BioLinkClassObject) {
     this._name = name;
     this._description = info.description;
-    this._id_prefixes = info.id_prefixes;
+    this.id_prefixes = info.id_prefixes;
     this._parent = typeof info.is_a === 'undefined' ? info.is_a : pascalCase(info.is_a);
     this._children = [];
   }
@@ -30,6 +28,16 @@ export default class Entity implements BioLinkEntityObject {
     return this._id_prefixes;
   }
 
+  set id_prefixes(idPrefixes: string[]) {
+    if (this._name === "Gene") {
+      this._id_prefixes = [...["SYMBOL", "OMIM", "UMLS"], ...idPrefixes];
+    } else if (this._name === "ChemicalSubstance") {
+      this._id_prefixes = [...["UMLS"], ...idPrefixes]
+    } else {
+      this._id_prefixes = idPrefixes;
+    }
+  }
+
   get name(): string {
     return this._name;
   }