Teacher: One page per learner, printed A4. Sections <b>A</b> and <b>B</b> count toward <b>Written Works</b>; see <code>assessment.md</code> §1. Item <b>★</b> is the diagnostic — every part of it can be got wrong by a learner who filled sections A and B perfectly, which is exactly what it is for. The key below is screen-only and will not print.
A Complete the crosses — write the four offspring genotypes for each
Cross
The four cells
Tt × Tt
TT × tt
Tt × tt
TT × Tt
tt × tt
B Both ratios, separately — T = tall is dominant, t = semi-dwarf is recessive
Cross
Genotype ratio
Phenotype ratio
Tt × Tt
Tt × tt
TT × Tt
C Same or different — tick one
Statement
True
False
A TT plant and a Tt plant look the same.
Dominant traits are always the more common ones.
In Tt, the t is damaged by the T.
Two tall parents can have a semi-dwarf offspring.
D Your own coin data — ten flips of two coins, from the lesson
My ten results
What the class's total was
The two boxes are the same size on purpose. Your ten and the class's four hundred are equally real data, and they will not agree.
★ The challenge — one family, four children
A couple are both <b>Tt</b> for a trait. They have four children and <b>all four</b> show the recessive trait. Has something gone wrong with the genetics? <span class="blank lg"></span>
Explain your answer using the word <b>chance</b>. <span class="blank lg"></span> <span class="blank lg"></span>
A farmer plants 400 seeds from the same cross. Would you expect the same surprise? <b>Why?</b> <span class="blank lg"></span> <span class="blank lg"></span>
Answer key — screen only, not printed.
<b>A</b> · TT, Tt, Tt, tt · Tt, Tt, Tt, Tt · Tt, Tt, tt, tt · TT, TT, Tt, Tt · tt, tt, tt, tt.<br><b>B</b> · 1 TT : 2 Tt : 1 tt and 3 tall : 1 semi-dwarf · 1 Tt : 1 tt and 1 : 1 · 1 TT : 1 Tt and all tall. <b>A learner who gives one ratio for both columns has not separated genotype from phenotype</b>, which is the second-commonest error of the week.<br><b>C</b> · True · <b>False</b> · <b>False</b> · True.<br><b>D</b> · varies. Almost nobody gets 3 and 1 in ten flips; the class total should be close to 3 : 1.<br><b>★ This is the diagnostic.</b> Item 1: <b>no</b> — nothing has gone wrong. Item 2: each child had an independent 1 in 4 chance; four in a row is unlikely but perfectly possible, about 1 in 256. Item 3: <b>no</b> — with 400 seeds the count will land close to 100, because large numbers of independent events settle near the ratio. <b>A learner who writes "something must be wrong" on item 1 has treated the ratio as a quota</b>, and that is the single most common misunderstanding of this competency among adults as well as children.