Explain4 marksStandard
In a plant species, flower colour is controlled by two unlinked genes. Gene P (alleles P and p) controls pigment production; P_ gives coloured flowers, pp gives white flowers. Gene Q (alleles Q and q) controls pigment deposition; Q_ allows deposition, qq prevents deposition even if pigment is present. A cross between two plants heterozygous for both genes (Pp Qq) was carried out. The F2 offspring are shown in the table:
| Phenotype | Number of plants |
|---|---|
| Coloured | 56 |
| Pale | 19 |
| White | 25 |
Explain the genetic basis of these results. Use a genetic diagram in your answer.