I'm drawing vertices in the editor as gizmo spheres however the positions are always stationary, never moving when I adjust the position or scale of the object it's attached to. Is there something I'm missing?

void OnDrawGizmosSelected () {

    MeshFilter selectedMeshFilter = (MeshFilter)gameObject.GetComponent("MeshFilter");
    Mesh mesh = selectedMeshFilter.mesh;
    Vector3[] vertices  = mesh.vertices;
    Color[] colors = new Color[vertices.Length];

    for (var i = 0  ; i < vertices.Length   ;   i++){

        Gizmos.DrawSphere (vertices[i], vertexSize);

    }
        mesh.vertices = vertices;
        mesh.RecalculateBounds();

}