Same answer chain

Use this to connect the question's starting point to the final result.

Use parent genotypes to identify possible gametes

Combine gametes to derive offspring genotypes

Map each offspring genotype to the affected or unaffected phenotype

State a probability that matches the derived offspring outcomes

Current question

A person with the genotype Dd and a person with the genotype dd plan to have a child. Determine the probability that the child will have polydactyly. You should: • complete the Punnett square diagram • identify any offspring genotype that would have polydactyly. Probability that the child will have polydactyly =

Use after you understand the chain

These resources explain how the links cause the effect and how examiners award marks.

Show model answer Open mark checklist

Try writing an answer using the chain first, then check it against the model and checklist.

Why this earns marks

1 Use parent genotypes to identify possible gametes.
2 Combine gametes to derive offspring genotypes.
3 Map each offspring genotype to the affected or unaffected phenotype.
4 State a probability that matches the derived offspring outcomes.

Common weak answer: Names the topic but skips the middle reasoning links.