Answer:
The nucleus.
Explanation:
The nucleus is basically "the boss" of DNA along with housing it. Hope this helps! 
 
        
             
        
        
        
1) ctg act gct aat (you are correct)
2) GAC UGA CGA UUA
* remember for mRNA, a pairs with u
3) Aspartic Acid (Asp), Arginine (Arg), Leucine (Leu)
4) substitution (t changed to g)
Explanation: from GAC TGA CGA TTA
 to GAC GGA CGA TTA
5) new mRNA strand: CUG CCU GCU AAU
6) yes, because the amino acids changed, which will code for different proteins. 
Hope that helped! And your teacher did a really bad job forming this question, like how there is no starting codon and (no clarity) you don’t know which DNA sequences to use.
        
                    
             
        
        
        
I think its B. Im not sure