When an artery gets a constricted region due to plaque, how does the pressure in this region compare to the pressure in an unconstricted region adjacent

Pressure increases.

Explanation:

When an artery gets a constricted region due to plaque, the pressure in this region increases as compared to the pressure in an un-constricted region where the pressure is normal because in the non-constricted region there is no narrow artery and the blood flows normally. When the artery becomes narrow due to deposition of any materials, the blood pressure increases so that's why we can say that the pressure increases in the artery in constricted region.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.