Not all of the human genome codes for proteins. Which of the following characteristics describes about 50 percent of the human genome?
genes that code for proteins
B sequences that regulate genes that code for proteins
C genes that code for RNA molecules
D highly repetitive sequences
E imprinted sequences

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.