<span>macromolecule, cell, tissue, organ, organ system</span>
        
                    
             
        
        
        
Nucleus can be defined as a large organelle found in the Eukaryotic cells and it is also  know as the cell's command center,thus it controls the activity of the cells 
Explanation:
- The answer to the above question is (c )nucleus. During the cell cycle the nucleus of the cell mediates the replication of the of the DNA and controls the gene expression.
- The nucleus contains a structure which is known as nucleolus and which is made up of protein and ribonucleic acid(RNA)
 
        
             
        
        
        
The right answer is The cells are damaged.
Take the example of skin cells.  
The skin consists of two tissues:
* the outermost, the epidermis, resting on a vascularized connective tissue,
* the dermis.
In the epidermis, which includes several layers of cells, the outer layer is formed of dead cells that are desquamating and are constantly being replaced from proliferating basal cell cells. So, in normal conditions, the epidermis is in constant renewal.
On the other hand, when accidentally, the upper parts of the epidermis are damaged, for example, a slight abrasion or of a burn, the destroyed portion is regenerated (replaced) thanks to an accelerated proliferation of basal epidermal cells .
 
        
                    
             
        
        
        
Explanation:
 When there is DNA shape mutation, one of the main things that could happend in the change of shape of the proteins, this creates a different pattern to arrange the nucleotids in the nuclei of the cells