Final answer:
One end of the DNA polynucleotide has a free 5' phosphate and the other end has an unbound 3' OH group, due to the sequence of phosphodiester bond formation between nucleotides. DNA synthesis occurs in a 5' to 3' direction, and the sugar-phosphate backbone forms the exterior of the DNA's double helix.
Step-by-step explanation:
When analyzing the structure of polynucleotides such as DNA, we observe that they have distinct ends due to the arrangement of their components. One end of the DNA polynucleotide will have a free 5' phosphate and the other end will have an unbound 3' OH group. This is because a polynucleotide chain is formed through the linkage of nucleotides via phosphodiester bonds, which connect the phosphate group at the 5'-carbon of one nucleotide to the hydroxyl group at the 3'-carbon of another nucleotide.
As a result, the chain has an unlinked triphosphate at the 5' end, and an unlinked -OH group at the 3' end. DNA synthesis proceeds from the 5' to 3' direction, with the sugar-phosphate backbone comprising the outside of the DNA's double helix structure and the nitrogenous bases stacking in the interior, forming base pairs and held together by hydrogen bonds.