Structure of phosphates in nucleotides
Well it turns out that when nucleotides are bonded together in a strand of DNA/RNA (nucleic acid) they ALWAYS HAVE only one phosphate group attached to their nucleoside (nucleoside = sugar + nitrogenous base (without phosphate)).

However, when they are by themselves, they are more often found with two or three phosphate groups as oppose to just the one. For this reason, the definition of a nucleotide is often misunderstood as it refers to containing one OR MORE phosphates, in reality, the official definition of a nucleotide states that only one phosphate group is present...

An example of a (so-called) "nucleotide" is ATP (adenosine triphosphate); it follows all of the rules that the misunderstood definition of a nucleotide states (these are; a nitrogenous base (adenine); a pentose sugar (ribose); and one "OR MORE" phosphate groups (triphosphate)). However, according to the official definition of a nucleotide, it is not, in fact, a nucleotide! It is instead considered a 'nucleoside triphosphate', since it is a nucleoside. with three phosphate groups (it is also a nucleotide with two additional phosphate groups, but I guess 'nucleotide-with-a-diphosphate' attachment doesn't roll off the tongue so well as nucleoside triphosphate).

Finally, as in nucleic acids and indeed anywhere else (according to the official definition of the nucleotide), there is only one phosphate group allowed to attached to each nucleoside (regular phosphate group) to form a nucleotide (officially). Therefore there is no variation allowed in the phosphate groups (since there's only one and they bond to other nucleotides, in the same way, every time (in nucleic acids)), furthermore in the pentose sugar the only variation allowed is whether it is a ribose (in RNA) or a deoxyribose (in DNA). So the phosphate-sugar backbone of the DNA strands and the RNA strands (nucleic acids) are consistent throughout the entire strand (and each strand of its type; differentiating only in the type of pentose sugar it consists of (ribose/deoxyribose)). Consequently, there is no phosphate-sugar backbone variation within DNA strands or RNA strands, for the phosphate or the pentose sugar to make any genetic difference to genetic material (those strands); only the nitrogenous bases and their sequences can make a difference to the genetic material...