There are 64 3 61 codons'

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There are 64 - 3 61 codons. This might imply
that there are 61 anticodons, and therefore 61
different tRNA molecules. Is this really the
case? There are actually fewer than 61 tRNA
molecules. A single anticodon (tRNA
molecule) can frequently pair with more than
one codon---partially explaining the degeneracy
of the code. The rules of WC base pairing are
relaxed for the 5 base of the anticodon
(corresponding to the 3 base of the codon).
This base is less constrained than the others, it
can form a greater variety of hydrogen bonds.
In Cricks terms, it can wobble.
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Wobble rules for codon-anticodon pairing in E.
coli Anticodon 5 prime base
Codon 3 prime base A
U
C
G U
A or G G
C or U
I
A or C or U
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The Central Dogma of molecular biology
DNA makes RNA makes protein
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Reverse transcription
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RNA
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BREAK TIME
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Mutations as inborn errors of metabolism
Archibald
Garrod, 1908 (see text p 9) One gene - one
enzyme
G.W. Beadle E.L. Tatum, 1940s One gene - one
polypeptide
(current understanding)
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CHEMICAL PROPERTIES OF R GROUPS 1. Aliphatic
(e.g. valine) 2. Aromatic (e.g. proline) -
hydrophobic 3. Acidic (e.g. glutamic acid) -
negative charge, hydrophilic 4. Basic (e.g.
arginine) - positive charge, hydrophilic 5.
Sulfhydryl group (e.g. cysteine) - disulphide
bonds
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