Persistent Copper Tolerance Expression (PCTE) is a trait observed in certain populations of the yellow monkeyflower (Mimulus guttatus) growing on soil contaminated with heavy metals near copper mines. Normally, expression of the copper-transporting gene, CpT1, is down-regulated as the plant matures to conserve metabolic energy. However, plants with PCTE continue to express this gene at high levels throughout adulthood, allowing them to survive in highly toxic soils. This trait is controlled by a dominant allele.
Describe how the presence of toxic copper contamination in the soil as a selective pressure could have led to an increase in the frequency of the PCTE trait in populations near mines.
Explain why the proportion of plants showing the PCTE phenotype would rapidly increase in a population once selection for this condition had been established.
PCTE is caused by a single point mutation in regulatory DNA. This mutation does not occur within the protein-coding sequence of the CpT1 gene.
Suggest and explain how this mutation causes PCTE.
