Final answer:
A substitution mutation in DNA, such as replacing cytosine with adenine, can disrupt the normal structure and function of DNA, leading to potentially harmful effects. For example, sickle cell disease is caused by a single amino acid substitution in hemoglobin protein, resulting in deformed red blood cells.
Step-by-step explanation:
A mutation occurs when cytosine is replaced with adenine in DNA. This type of mutation, known as a substitution mutation, can have impacts on the structure of DNA. Specifically, the change in base pairing can disrupt the normal double helix structure of DNA, affecting its stability and ability to function properly.
For example, in the case of sickle cell disease, a single amino acid substitution in the protein hemoglobin alters its structure, causing the red blood cells to deform and break. This demonstrates how even a small change in structure can have a significant impact on the function and overall health of an organism.