<span>The most crucial principle of ELISA (enzyme-linked immunosorbent assay) is a highly specific antibody-antigen interaction.</span> 
ELISA is a biochemical technique used to detect the presence of an antibody or an antigen in the biological sample. Simply described, in an ELISA, an antigen is immobilized on a solid surface and then a specific antibody is applied over the surface so that it can bind to the antigen. The antibody is usually linked to an enzyme, and in the final step, a substrate for that enzyme is added. The enzyme can convert it to some detectable signal, most commonly a color change. <span>Medical usage of ELISA is in the diagnosis of HIV infection, pregnancy tests, measurement of cytokines…</span>
        
             
        
        
        
Answer:
From CARBONDIOXIDE (CO2) found in the atmosphere
Explanation:
Photosynthesis is a process performed by autotrophic organisms like green plants. It is a phenomenon whereby these plants manufacture their own food (sugars) using an inorganic carbon source in the presence of sunlight to provide energy. 
The major end product of photosynthesis is glucose, which has a carbon constituent i.e. C6H12O6. However, this carbon needed to make glucose is got from an inorganic molecule called CARBON DIOXIDE, which the plants take from the atmosphere in via the stomata on their leaves.
 
        
             
        
        
        
Answer:
mutation
Explanation:
occurs when a DNA gene is damaged or changed in such a way a to alter the genetic message carried by that gene. A mutation is an gent of substance that can bring about permanent alteration to the physical composition of a DNA gene such that the genetic message is changed
 
        
             
        
        
        
Answer:
The executive branch carries out and enforces laws. It includes the President, Vice President, the Cabinet, executive departments, independent agencies, boards, commissions, and committees.
 
        
             
        
        
        
The correct answer is S phase