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sub90 ESATsub90 ESAT SyllabusARCH-B-07
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UAT-UK SPEC: B6MODULE: BIOLOGYTOPIC ID: ARCH-B-07

Recombinant DNA: Restriction Endonucleases, Sticky Ends, Ligase & Plasmid Marker Screening

Master Recombinant DNA: Restriction Endonucleases, Sticky Ends, Ligase & Plasmid Marker Screening on the ESAT Biology paper. Traditional classroom derivations waste valuable seconds. Using the 2-step Sub-90 invariant elimination method compresses solve time to 35s, saving +95s per question.

Standard Classroom Time
130s
Textbook multi-line derivations bleed exam clock
Sub-90 Target Pace
35s
Comfortably below the 88.8s per-question limit
Time Saved for Review
+95s
Banks clock buffer across 27 questions

2-Step Sub-90 Shortcut Formula

How to eliminate intermediate algebra and solve under 45 seconds.

Launch Interactive Lesson
STEP 1 • SETUP INVARIANT (LINE 1)10–15s
Classic ESAT trap: Ligase = Phosphodiester backbone, NOT hydrogen bonds   ⟹  \implies eliminate 3 immediately   ⟹  \implies 1 and 2 only.

Establish the structural invariant and eliminate impossible options immediately.

STEP 2 • FAST SOLVE (LINE 2)15–25s
Classic ESAT trap: Ligase = Phosphodiester backbone, NOT hydrogen bonds   ⟹  \implies eliminate 3 immediately   ⟹  \implies 1 and 2 only.

Evaluate the simplified expression using integer factoring or unit elimination.

Distractor Trap Forensics

The predictable cognitive traps engineered by examiners into the wrong options.

TRAP #1multi_statement_linchpin_foil

Swapping restriction endonuclease (cuts phosphodiester backbone at specific recognition sequence) with DNA ligase (joins sugar-phosphate backbone via phosphodiester bonds)

Confusing the cutting enzyme with the joining enzyme, or claiming ligase forms hydrogen bonds between bases (hydrogen bonds form spontaneously!).

Sub-90 Fix: Test invariants before expanding equations.
TRAP #2fence_post_or_domain_trap

Cutting a circular plasmid at n restriction sites and getting n+1 fragments instead of n fragments (versus n+1 fragments for a linear DNA molecule)

Fence-post topology trap: n cuts on a closed circle give n fragments; n cuts on a linear strand give n + 1 fragments.

Sub-90 Fix: Test invariants before expanding equations.
TRAP #3sign_or_direction_flip

Selecting bacteria that GROW on tetracycline when the foreign gene was inserted INTO the tetracycline-resistance gene (insertional inactivation)

Successful recombinant plasmids have their second antibiotic resistance gene disrupted, so they grow on Ampicillin but DIE on Tetracycline.

Sub-90 Fix: Test invariants before expanding equations.

Try 1 Timed Question: Recombinant DNA: Restriction Endonucleases, Sticky Ends, Ligase & Plasmid Marker Screening

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Full Lesson All 15 Questions (ARCH-B-07)
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ARCH-B-07: Recombinant DNA: Restriction Endonucleases, Sticky Ends, Ligase & Plasmid Marker Screening (Sample)Biology
00:00.0
SUB-90 ZONE (<30S)
0.0s30s Sub-9090s ESAT Budget150s Classroom
Question 1 of 1ARCH-B-07 (6-Card Lesson)Format: 1-2-3 Multi-Statement Combination
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Question 1 of 1 • 90s Target

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Biology•ARCH-B-07•1-2-3 Multi-Statement
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