Question

Which step of Koch's postulates is incorrect? A. 1.The pathogen is first found in an infected, unhealthy person.B. 2.The pathogen is isolated from an unhealthy person and grown in a lab.C. 3.The pathogen grown in a lab will be given to a healthy organism that gets the same disease.D. 4.The pathogen should be isolated again and should have mutated when compared to the original.

Answer 1

Let's analyze each one of the postulates and compare to the options.

1. A pathogen must be found in the body of a sick person.

This one states the same as the option A, therefore option A is not the answer.

2. A pathogen must be isolated and grown in a lab culture.

This one states the same as the option B, therefore option B is not the answer.

3. The pathogens that were created in this lab culture, when introduced in a healthy person's body, must give the disease to this person.

This one states the same as the option C, therefore option C is not the answer.

4. The pathogen must be isolated again and must be the same as the original.

This one states that the last isolated pathogen must be equal to the original one, but option D states that it must be mutated, which means that it would be different than the original. Therefore, option D is incorrect.

The correct answer is D. 4.The pathogen should be isolated again and should have mutated when compared to the original.