Final answer:
Erwin Chargaff discovered that the quantity of adenine is always similar to thymine, and the quantity of guanine is similar to cytosine in DNA, known as Chargaff's rules, which was essential for the discovery of DNA's double-helix structure.
Step-by-step explanation:
Erwin Chargaff's Discovery on DNA
The feature regarding DNA that Erwin Chargaff discovered pertains to the concentrations of the nitrogen bases within the DNA molecule. In the mid-1900s, Chargaff studied DNA from various species and made seminal observations.
He noticed that while the quantities of the four nitrogen bases—adenine (A), guanine (G), cytosine (C), and thymine (T)—vary from one species to another, each species maintains a specific pattern: the concentration of adenine is always similar to that of thymine, and the concentration of guanine is similar to that of cytosine.
This finding is encapsulated in what are now known as Chargaff's rules. Chargaff's rules essentially state that A = T and G = C within the DNA of an organism.
This was crucial information that helped later researchers, such as Watson and Crick, to deduce the double-helix structure of DNA.
The consistency of these base pairing ratios was a key piece of the puzzle, indicating that A pairs with T and G pairs with C, governed by hydrogen bonding, and that these bonds are optimal when the two DNA strands run in opposite directions, or antiparallel.
Moreover, Chargaff's findings highlighted that DNA's composition is species-specific but consistent within a species, providing insights that bolstered the understanding that DNA is the genetic material of cells.
This knowledge greatly contributed to the scientific community's ability to sequence DNA and understand genetic coding and replication.