Which of the following best describes a significant application of biotechnology in healthcare?

The development of gene therapy is a significant application of biotechnology in healthcare because it focuses on treating or preventing diseases by directly modifying or manipulating genes. This innovative approach holds the potential to address genetic disorders, some cancers, and other illnesses by replacing, inactivating, or introducing genes into a patient's cells. Gene therapy aims to correct the underlying genetic causes of diseases rather than merely alleviating symptoms, marking a transformative shift in healthcare that can lead to long-lasting solutions for previously untreatable conditions.

In the context of the other options, while animal breeding can enhance efficiency, it primarily falls under agricultural biotechnology rather than healthcare. Crop enhancement for food security is essential for addressing nutritional needs and sustainable agriculture but does not directly relate to improving human health outcomes. Pest control through biological means is also a vital aspect of biotechnology, focusing on agricultural pests and environmental sustainability rather than human health issues. Thus, gene therapy stands out as uniquely pertinent and impactful within the healthcare landscape.