Trap 1: Direction of Synthesis vs Direction of Template Reading

Error: Saying DNA polymerase synthesizes 3'→5'. Correct: DNA polymerase ALWAYS synthesizes 5'→3'. It READS the template 3'→5'. Both leading and lagging strands are synthesized 5'→3'.

Trap 2: Repressor Binds Promoter (not Operator)

Error: The Lac repressor binds the promoter to block RNA polymerase. Correct: The repressor binds the OPERATOR (a DNA sequence between promoter and structural genes). The promoter is where RNA polymerase binds.

Trap 3: Lactose vs Allolactose as Inducer

Error: "Lactose is the inducer of the Lac operon." Correct: Allolactose (an isomer of lactose, formed by beta-galactosidase) is the true inducer. Lactose itself is converted to allolactose, which then binds the repressor.

Trap 4: H1 is Part of the Histone Octamer

Error: The histone octamer contains H1. Correct: The octamer = 2×H2A + 2×H2B + 2×H3 + 2×H4 = 8 histones. H1 is the LINKER histone — outside the core particle.

Trap 5: Super-Repressor = Constitutively ON

Error: A repressor mutant that cannot bind allolactose leads to constitutive expression (always ON). Correct: This produces a super-repressor (always bound to operator) → constitutively OFF. Constitutive ON = operator mutation preventing repressor binding.

Trap 6: RNA Polymerase Needs a Primer

Error: RNA polymerase needs a primer (like DNA polymerase). Correct: RNA polymerase does NOT need a primer. It can initiate de novo. Only DNA polymerase requires a primer.

Trap 7: Dispersive vs Semiconservative in Meselson-Stahl

Error: After 2 generations, dispersive and semiconservative both give the same results. Correct: After 2 generations, semiconservative gives 2 bands (hybrid + light); dispersive would give only 1 band at intermediate density. The appearance of the light band rules out dispersive replication.

Trap 8: Chargaff's Rules Apply to Single-Stranded DNA

Error: In any DNA molecule, A = T and G = C. Correct: Chargaff's rules apply ONLY to double-stranded DNA. In single-stranded DNA (or in individual strands), A ≠ T and G ≠ C are perfectly possible.