Anticoagulant rodenticides are widely used to control brown rat (Rattus norvegicus) populations. These poisons inhibit the enzyme vitamin K epoxide reductase (VKOR), which is essential for blood clotting. Some rat populations have evolved a trait known as Hereditary Anticoagulant Resistance (HAR), which is controlled by a dominant allele.
Describe how the widespread use of anticoagulant rodenticides as a selective pressure could have led to an increase in the frequency of the HAR trait in certain rat populations.
Explain why the proportion of rats showing the HAR phenotype would rapidly increase in a population once selection for this condition had been established.
HAR can be caused by a point mutation in the regulatory DNA. This mutation does not occur within the protein-coding sequence of the Vkorc1 Vkorc1\,Vkorc1 gene (the gene encoding the VKOR enzyme).
Suggest and explain how this mutation causes HAR.
