75-Archetype SyllabusBiology • ARCH-B-06 • Spec B5

Full 6-Card Lesson 15-Question Timed Drill

UAT-UK SPEC CODE: B5 (DNA)ASSUMED MATHS 1 PREREQUISITE: M3.5FREQUENCY: VERY HIGH

DNA Base Composition (%A = %T, %G = %C), Triplet Coding Ratios & Point Mutations

Deconstructed from 19 past UAT-UK questions (8.15% of all historical Biology papers). Students using standard A-Level classroom methods spend an average of 125s on this archetype—blowing past the 90s ESAT budget. Using the 2-line Sub-90 heuristic below compresses solve time to 30s (saving 95s per question).

Historical Frequency

19 Past Qs

8.15% of Biology

Classroom Trap Time

125s

+35s over 90s budget

Sub-90 Target Time

30s

Banks +95s on the clock

Dominant UI Format

5-Option A–E

Maths 1 Skill: M3.5

Card 1 & Card 2 Preview: The Classroom Time Trap vs. Sub-90 2-Line Rule

Excerpted from our interactive 6-Step Topic Lesson for ARCH-B-06.

Launch All 6 Active-Recall Cards

CARD 1 OF 6 • THE CLASSROOM TIME TRAP (125s)

Why Students Bleed Time:

In double-stranded DNA, base pairing ensures

\%\text{A} = \%\text{T} = 18\%

, so

\text{A} + \text{T} = 36\%

. The remaining

100\% - 36\% = 64\%

is split equally between

\text{G}

and

\text{C}

, giving

\%\text{G} = \frac{64\%}{2} = 32\%

(~90s).

In 19 past UAT-UK questions (8.15% of Biology), candidates lose 95s by forgetting to subtract both %a and %t (2 * 20% = 40%) from 100% before halving for %g. Instead, apply B5 with Maths 1 skill M3.5.

CARD 2 OF 6 • THE 2-LINE SUB-90 HEURISTIC (<30s)

Line 1 (50% Purine-Pyrimidine Invariant): In dsDNA,

\%\text{A} + \%\text{G} = 50\%

ALWAYS.

Line 2 (Subtract):

\%\text{G} = 50\% - 18\% = 32\%

(10s).

Sanity & Limit Check: Verify units/signs against factor_of_two_or_stoichiometry_trap (Calculating %G in double-stranded DNA with 20% A as (100 - 20)/2 = 40% instead of (100 - 40)/2 = 30%) and fence_post_or_domain_trap (Applying %A = %T to a SINGLE strand of DNA or mRNA instead of double-stranded DNA).

Examiner Distractor Blueprint for ARCH-B-06

FOIL #1factor_of_two_or_stoichiometry_trap

Calculating %G in double-stranded DNA with 20% A as (100 - 20)/2 = 40% instead of (100 - 40)/2 = 30%

Forgetting to subtract BOTH %A and %T (2 * 20% = 40%) from 100% before halving for %G.

Open Factor-of-2 / Stoichiometry Clinic

FOIL #2fence_post_or_domain_trap

Applying %A = %T to a SINGLE strand of DNA or mRNA instead of double-stranded DNA

Chargaff's rule (%A = %T, %G = %C) holds globally across the double helix, not within a single strand unless specified.

Open Fence-Post / Domain Trap Clinic

FOIL #3factor_of_two_or_stoichiometry_trap

Dividing by 3 instead of multiplying by 3 when converting amino acids to coding DNA bases (or confusing base pairs with total bases = 2 * base pairs)

1 amino acid = 3 mRNA bases = 3 template DNA bases = 6 bases across both DNA strands.

Open Factor-of-2 / Stoichiometry Clinic

FOIL #4multi_statement_linchpin_foil

Claiming every base substitution mutation changes the amino acid sequence (ignoring the degenerate genetic code)

Because the triplet code is degenerate, a silent base substitution can still code for the exact same amino acid.

Open Multi-Statement Linchpin Foil Clinic

Try 1 Live Sample Question Under the 90-Second Stopwatch

Press W to open the 2-line dry-wipe scratchpad, select A–E, and lock in to reveal the Dual-View solution.

Full 6-Card Lesson Launch All 15 Questions (ARCH-B-06)

ARCH-B-06: DNA Base Composition (%A = %T, %G = %C), Triplet Coding Ratios & Point Mutations (Sample)Biology

00:00.0

SUB-90 ZONE (<30S)

0.0s30s Sub-9090s ESAT Budget150s Classroom

Question 1 of 1ARCH-B-06 (6-Card Lesson)Format: Standard 5-Option

Right-click any option to cross out • Keys A–E + Enter

Question 1 of 1 • 90s Target

Ready to Start Question 1?

The question stem, diagram, and answer options are hidden behind this pre-start gate. When you click below, the question will reveal and your 90-second split stopwatch will immediately begin ticking.

Biology•ARCH-B-06•Standard 5-Option

or press Enter to start