UAT-UK SPEC CODE: B4 (Inheritance)ASSUMED MATHS 1 PREREQUISITE: M7.7FREQUENCY: MEDIUM
Non-Mendelian Ratios (2:1 Lethal Alleles, Codominance, Dihybrid & Multi-Cross Phenotypic Ratio Tables)
Deconstructed from 5 past UAT-UK questions (2.15% of all historical Biology papers). Students using standard A-Level classroom methods spend an average of 130s on this archetype—blowing past the 90s ESAT budget. Using the 2-line Sub-90 heuristic below compresses solve time to 35s (saving 95s per question).
Historical Frequency
5 Past Qs
2.15% of Biology
Classroom Trap Time
130s
+40s over 90s budget
Sub-90 Target Time
35s
Banks +95s on the clock
Dominant UI Format
Table Matching
Maths 1 Skill: M7.7
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-05.
CARD 1 OF 6 • THE CLASSROOM TIME TRAP (130s)
Why Students Bleed Time:
Two living yellow mice must both be heterozygous (), because is lethal. The zygote ratio is . Since embryos die in utero, the surviving live-born ratio is , so of live offspring are yellow (~105s).
In 5 past UAT-UK questions (2.15% of Biology), candidates lose 95s by group a has a-antigens on rbcs and anti-b antibodies in plasma (having anti-a would agglutinate its own blood!). Instead, apply B4 with Maths 1 skill M7.7.
CARD 2 OF 6 • THE 2-LINE SUB-90 HEURISTIC (<35s)
**Line 1 (Lethal Signature):** ( survive).
Line 2 (Live Fraction): (20s).
Sanity & Limit Check: Verify units/signs against
sign_or_direction_flip (Swapping red blood cell surface antigens with plasma antibodies (e.g. saying Group A has anti-A antibodies)) and fence_post_or_domain_trap (Assuming Group A x Group B parents can only produce A, B, or AB offspring (forgetting I^A I^O x I^B I^O -> 1/4 I^O I^O Group O)).Examiner Distractor Blueprint for ARCH-B-05
FOIL #1sign_or_direction_flip
Swapping red blood cell surface antigens with plasma antibodies (e.g. saying Group A has anti-A antibodies)
Group A has A-antigens on RBCs and anti-B antibodies in plasma (having anti-A would agglutinate its own blood!).
FOIL #2fence_post_or_domain_trap
Assuming Group A x Group B parents can only produce A, B, or AB offspring (forgetting I^A I^O x I^B I^O -> 1/4 I^O I^O Group O)
Assuming homozygous I^A I^A instead of heterozygous I^A I^O.
FOIL #3sign_or_direction_flip
Reversing universal donor (Group O: no A/B antigens on RBCs) and universal recipient (Group AB: no anti-A/anti-B antibodies in plasma)
Matching donor antibodies against recipient cells instead of donor RBC antigens against recipient plasma antibodies.
FOIL #4table_column_pruning_trap
Evaluating all 4 blood group crosses before checking the Group AB or Group O row (which has a unique 1-to-1 genotype)
Group O is strictly I^O I^O and Group AB is strictly I^A I^B—check those columns first.
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.
sub90 ESATARCH-B-05: Non-Mendelian Ratios (2:1 Lethal Alleles, Codominance, Dihybrid & Multi-Cross Phenotypic Ratio Tables) (Sample)Biology
00:00.0
SUB-90 ZONE (<35S)
0.0s35s Sub-9090s ESAT Budget150s Classroom
Right-click any option to cross out • Keys
A–E + EnterQuestion 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-05•Standard 5-Option
or press Enter to start