Trap 1 — Direction of synthesis: DNA polymerase ALWAYS synthesizes 5'→3'. It READS the template 3'→5'. Students confuse these two directions. Both leading and lagging strands are synthesized 5'→3'.

Trap 2 — Primer requirement: DNA polymerase NEEDS a primer (RNA primer from primase). RNA polymerase does NOT need a primer — it initiates transcription de novo at the promoter.

Trap 3 — Lac operon inducer: Allolactose (NOT lactose) is the inducer. Lactose is first converted to allolactose by beta-galactosidase. This frequently appears as a trap.

Trap 4 — Repressor binds operator (not promoter): The lac repressor binds the OPERATOR. RNA polymerase binds the PROMOTER. Confusing these two sites is the most common Lac operon error.

Trap 5 — Nucleosome vs H1: The octamer = H2A, H2B, H3, H4 (2 copies each). H1 is the LINKER histone — NOT part of the octamer. Questions often list H1 as an octamer component.

Trap 6 — Super-repressor direction: A lacI mutation preventing allolactose binding creates a super-repressor that is always ON the operator → genes constitutively OFF. Not constitutively expressed (ON).

Trap 7 — Chargaff's rules apply only to dsDNA: In single-stranded DNA, A ≠ T and G ≠ C. Students incorrectly apply Chargaff's rules to single-stranded nucleic acids.

Trap 8 — 32P and 35S labelling: ^32P labels DNA (phosphate backbone); ^35S labels protein (sulfur in amino acids). Students often confuse which isotope labels which molecule.

Trap 9 — Stop codon recognition: Stop codons are recognized by RELEASE FACTORS (proteins), not by tRNAs.

Trap 10 — HGP numbers: ~20,000–25,000 genes (NOT 100,000 as originally predicted); 3.2 billion base pairs (NOT million).