CAIE A Level Biology 9700 · Inheritance
In a species of plant, flower colour is determined by two unlinked genes, A and B. Alleles: A (dominant) and a (recessive); B (dominant) and b (recessive). A cross between two plants, both heterozygous at both loci (AaBb), produced the following offspring:
| Phenotype | Number of offspring |
|---|---|
| Red | 180 |
| Yellow | 60 |
| White | 80 |
Describe the inheritance pattern shown by these results.
6 marks, so the mark scheme is looking for about 6 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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