Final answer:
The claim regarding the equality of adenine to thymine and guanine to cytosine in DNA is correct and is based on Chargaff's rules. Although the ratio is consistent, the overall base composition varies among different species. These findings were instrumental in discovering the DNA double helix structure.
Step-by-step explanation:
The claim that in the DNA of both eukaryotes and prokaryotes, the amount of adenine (A) equals the amount of thymine (T) and the amount of guanine (G) equals the amount of cytosine (C) is accurate. This is based on Chargaff's rules, which state that DNA from any cell of all organisms should have a 1:1 ratio (base pair rule) of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. However, it's important to note that the overall base composition of DNA varies among different species.
The discovery by Erwin Chargaff reported variances in the relative concentrations of these four nucleotide bases from one species to another, contributing to the diversity of DNA sequences found in nature. Chargaff's findings were crucial in helping James Watson and Francis Crick determine the double helix structure of DNA, as the base pairing explained how genetic information is stored and replicated in cells.