Why is understanding the structure of dna and how it is replicated important? list some technologies and practical applications that could not have been developed without this understanding.

The discovery of DNA, as well as understanding of its functioning and structure, may well be the most essential findings of the last century.  

The impact of the discovery of DNA on medical and scientific advancement has been huge, whether it involves the manufacturing and creation of drugs to cure the deadly diseases or to identify the genes, which stimulate several of the diseases.  

The understanding of DNA and its structural composition has led to the discovery of various technologies that helps in the fields like genetic testing, identifying viruses, crime investigation, production of genetically modified organisms, and various others.  

i think that d. wind is the answer.   i missed the question when i answered a. currents.