Correct Option: D

If we look at the dermis, the layer on the skin beneath the epidermis (outer layer), and a certain type of cell within this layer, called a fibroblast, we find that the fibroblasts in the soles and palms secrete higher levels of a protein known as dickkopf 1, or DKK1, than the fibroblasts in the dermis at other body sites. It is believed that the rich source of DKK1 in these areas affects the epidermal layer above it and creates the physical characteristics of thickened, paler skin. DKK1 thickens the epidermis by increasing the number of skin cells and their density. Three genes affected by DKK1 – keratin 9, a KLEIP and a-catenin – have been found to cause this thickening. Keratin 9 reinforces the skin against physical impact, a KLEIP aids in cell division (multiplying) and makes cells smaller and, finally, a reduction in a-catenin is also possibly involved in cell contraction (making the cells more compact).