Final answer:
The phosphate group is normally found at the 5' end of a DNA strand and is a crucial component of the DNA structure that forms part of the backbone, providing the strand with directionality.
Step-by-step explanation:
The structure normally found on the 5' end of a DNA strand is the phosphate group. This is because nucleotides in DNA are linked together via phosphodiester bonds between the 5' phosphate group of one nucleotide and the 3' hydroxyl group of another. Therefore, a DNA strand has a free phosphate group at the 5' end. The 5' and 3' ends of a nucleic acid strand help to determine the directionality of the strand, which is crucial during DNA replication and other cellular processes where the sequence and orientation of the nucleic acid strands are important.
The phosphate group attached to the 5' carbon of the sugar in the nucleotide is part of the backbone of the DNA, whereas the nitrogenous base is attached to the 1' carbon of the sugar and protrudes from the backbone. The structure of DNA is such that the sugar and phosphate form the backbone, with the nitrogenous bases sticking out to engage in hydrogen bonding with their complementary bases, stabilizing the double helix structure.