How Chargaff’s Data Falsified the Tetranucleotide Hypothesis
- Erwin Chargaff’s chemical analyses of DNA showed that base composition varies among species and follows consistent pairing patterns (A=T, G=C).
- These results falsified the earlier tetranucleotide hypothesis, illustrating how science advances through falsification rather than proof.
The Problem of Induction
Definition
Induction
A way of reasoning where general principles are drawn from specific observations.
Example
Observing many white swans and concluding “all swans are white.”
- The problem is that no number of consistent observations can guarantee truth. one black swan disproves the claim.
- This is known as the problem of induction.
Scientific theories can never be proven absolutely true, only supported until contradictory evidence arises.
The Certainty of Falsification
Definition
Falsification
The idea that a hypothesis must make testable predictions that can be proven false by evidence.
- If a prediction fails, the hypothesis must be rejected or revised.
- So, if induction collects evidence; falsification tests it.
The Tetranucleotide Hypothesis
- In the early 1900s, scientists proposed that DNA was made of a repeating sequence of four nucleotides (A, T, G, C) in equal proportions.
- If this were true, DNA would be too simple to encode genetic information, so proteins were believed to be the genetic material instead.
- Assuming early scientists already knew DNA had complex coding capacity, they didn’t.
- Many things that seem obvious to us today were not obvious at the time.
Chargaff’s Findings
- By chemically analyzing DNA from many species, Chargaff discovered:
