Answer;
-Because the chemical groups that form hydrogen bonds are in the wrong positions.
Explanation; 
-A base pair is any of the pairs of nucleotides connecting the complementary strands of a molecule of DNA or RNA and consisting of a purine linked to a pyrimidine by hydrogen bonds. 
-The base pairs are adenine-thymine and guanine-cytosine in DNA, and adenine-uracil and guanine-cytosine in RNA or in hybrid DNA-RNA pairing. A mutation in the sequence of DNA that makes an adenine to be paired with a cytosine results to an unstable interaction because the chemical groups that form hydrogen bonds are in the wrong positions.
 
        
             
        
        
        
The fertilizers used by farmers can have negative effects on aquatic ecosystems because there is every possibility that the runoffs from the fields can create an algal bloom in the nearby water body. This algal bloom can have a very negative effect on the living organisms of the aquatic body. I hope it helps.
        
             
        
        
        
Answer:
Sistemas orgánicos
Explanation:
Aunque cada órgano del cuerpo realiza sus funciones específicas, los órganos también funcionan juntos por grupos, a los que se denomina sistemas orgánicos (ver Principales sistemas orgánicos). Los médicos clasifican las enfermedades y sus propias especialidades médicas de acuerdo a los diferentes sistemas orgánicos.
 
        
             
        
        
        
Ear muscles and tailbones are examples of vestigial structures found among the <span>Caminalcules. </span>