Identify the flow of information according to the "Central Dogma" of Molecular biology:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → DNA → mRNA → Protein
The central dogma, proposed by Francis Crick, says that genetic information flows from DNA to RNA to protein: DNA is transcribed into mRNA, and mRNA is translated into protein.
Option (1) mRNA → Protein → DNA — Incorrect. Information does not flow from protein back to DNA.
Option (2) mRNA → tRNA → RNA — Incorrect. tRNA is only an adapter in translation; it is not a step in the flow.
Option (3) DNA → mRNA → Protein — Correct. DNA is first copied into mRNA (transcription), and the mRNA is then read to make the protein (translation). This one-way order, DNA to RNA to protein, is the flow of information Crick called the central dogma.
Option (4) Protein → mRNA → DNA — Incorrect. This order runs the flow backwards, from protein to mRNA to DNA. In the central dogma information passes from DNA to RNA and then to protein; protein never serves as the template for RNA or DNA.
NCERT Extract:
Structure of Polynucleotide Chain – “… The proposition of a double helix structure for DNA and its simplicity in explaining the genetic implication became revolutionary. Very soon, Francis Crick proposed the Central dogma in molecular biology, which states that the genetic information flows from DNA→RNA→Protein.”