Why is the MeshFilter being removed?

Hi.. I´m trying to generate a 2D terrain (like terraria) with perlin Noise.

This is my Code:

 using UnityEngine;
 using System.Collections;
 
 public class NoiseMaker : MonoBehaviour {
     
     public GameObject Dot;
     public Mesh Dotmesh;
     public int InBetween = 4;
     
     private Color pixelcolor;
     private Texture2D noiseTex;
     private float newy;
     
     private GameObject[] Dot2 = new GameObject[1025];
     private Vector2 meshsize;
     
     // Use this for initialization
     void Start() {
         Dotmesh = Dot.GetComponent<MeshFilter>().mesh;
         meshsize = new Vector2(Dotmesh.bounds.size.x, Dotmesh.bounds.size.y);
         noiseTex = renderer.material.mainTexture as Texture2D;
         
         //noiseTex.GetPixels(x,y);
         for(int sizex = 1; sizex<1025; sizex++){
             Dot2[sizex] = Instantiate (Dot, new Vector3(sizex,0,0), Quaternion.identity) as GameObject;
                 
             newy = noiseTex.GetPixel(sizex, 1).grayscale * 10.0f;
             newy = Mathf.RoundToInt(newy);
             Debug.Log(newy);
                 
             Dot2[sizex].transform.position = new Vector3(Dot2[sizex].transform.position.x, newy, 0);
         }
     }
 }

It works on the first run. But it seems like the MeshFilter of "Dot" gets removed.. the prefab only shows a "missing mesh"... Like the GetComponent deletes the Filter ._.

Why is this happening?