Final answer:
Chargaff's data is used to calculate the ratio of nucleotide bases in DNA, which helps scientists understand the structure and function of DNA in different organisms.
Step-by-step explanation:
Chargaff's data is used to calculate the ratio of nucleotide bases in DNA. Chargaff observed that the ratios between A and T and between G and C in DNA are always approximately equal. This observation, known as Chargaff's rules, became an important piece of evidence for Watson and Crick in proposing their model of the DNA double helix. By knowing the ratios of the nucleotide bases, scientists can better understand the structure and function of DNA in different organisms.