We always say that enzymes are very specific to their substrates, then DNA polymerase can utilize all 4 types of nucleotides as substrates. to which substrate the DNA polymerase is specific?

Answer 1

Evolution has driven the specificity of DNA polymerase to recognize DNA nucleotides (nucleoside triphosphates) and not closely related RNA nucleotides (ribonucleoside triphosphates). Recognition of the 5 carbon sugar is key to this specificity as the nitrogenous bases and phosphates are also part of the RNA nucleotides.