How did James Watson and Francis Crick contribute to the understanding of DNA structure? a) They obtained a cell-free extract containing the tran...

James Watson and Francis Crick contributed to the understanding of DNA structure by interpreting the X-ray diffraction photograph taken by Rosalind Franklin. This photograph, known as Photo 51, provided crucial insights into the helical structure of DNA. Their interpretation of the photograph led to the proposal of the double helix model for DNA, which revolutionized our understanding of genetics and laid the foundation for modern molecular biology. Therefore, the correct answer is option d) They interpreted the X-ray diffraction photograph taken by Rosalind Franklin.