Current Pair
G : C
Watson-Crick (standard)
Standard Watson-Crick base pairing: G in anticodon pairs with C in codon via 3 hydrogen bonds.
This is the canonical, wobble-position-independent pairing.
Wobble Rule (Crick 1966)
The 3rd codon position (wobble position) allows non-standard pairing:
Anticodon 5' base → Codon 3' base it can pair with:
G → C or U (wobble)
U → A or G (wobble)
I (inosine) → C, U, or A (3 codons!)
C → G only
A → U only
Anticodon 5' base → Codon 3' base it can pair with:
G → C or U (wobble)
U → A or G (wobble)
I (inosine) → C, U, or A (3 codons!)
C → G only
A → U only
Why It Matters
Only ~45 tRNAs exist in humans, but there are 61 sense codons.
Wobble pairing allows each tRNA to recognize 2–3 codons.
Inosine (from A deamination by ADAT enzyme) lets one tRNA cover 3 codons.
This is why the genetic code is degenerate but not random.
Standard H-bond (Watson-Crick)
Wobble H-bond (shifted geometry)
Inosine pairing