1. Stop Codons — "U Are Amazing, U Are Gone, U Go Away"

• UAA = "U Are Amazing" (ochre)
• UAG = "U Are Gone" (amber)
• UGA = "U Go Away" (opal)
• Pattern: All start with U; contain A and/or G only.

2. Histone Octamer — "H2A, H2B at the Start; H3, H4 from the Heart (2 each)"

• 2 × H2A + 2 × H2B + 2 × H3 + 2 × H4 = 8
• H1 = "the One that's alone" (linker histone, not in octamer)

3. Meselson-Stahl Generations — "1=All Hybrid; 2=Half-Hybrid Half-Light"

• 1 generation → ALL hybrid density (all molecules have one ^15N + one ^14N strand)
• 2 generations → 50% hybrid + 50% light (2:2 ratio)

4. Lac Operon Structural Genes Order — "Zoo Yesterday Afternoon"

• lacZ → lacY → lacA

5. Replication Enzymes — "HElicase Primes the POLymerization, LIGAture Joins"

• Helicase → unwinds
• Primase → RNA primer
• Pol III → main synthesis
• Pol I → primer removal + gap fill
• Ligase → seals nicks

6. Central Dogma — "Don't Really Panic"

• DNA → RNA → Protein

7. Purines vs Pyrimidines — "PURe As Gold" (PUR = purines: A and G)

• PURines: Adenine and Guanine (double ring)
• CUT the PYrimidines: Cytosine, Uracil, Thymine (single ring)

8. Ribosome Sites — "APE" (A→P→E)

• A-site = Arrival (aminoacyl-tRNA enters)
• P-site = Peptide bond (growing chain)
• E-site = Exit (empty tRNA leaves)

9. Chargaff's Quick Calculation Trick

• If A = x%, then T = x%, G = C = (50 − x)%

10. Hershey-Chase — "Phosphorus in Pellet, Sulfur in Supernatant"

• ^32P → Pellet (bacteria) = DNA went IN
• ^35S → Supernatant = Protein stayed OUT