CAIE A Level Biology 9700 · Inheritance
A farmer crossed a pea plant that was heterozygous for two genes, A and B (genotype AaBb), with a plant that was homozygous recessive for both genes (aabb). The offspring phenotypes and their numbers are shown in the table.
| Phenotype | Number |
|---|---|
| AB | 382 |
| Ab | 38 |
| aB | 42 |
| ab | 338 |
Describe how these data can be used to determine whether the two genes are linked or unlinked.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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