Question

what does 5' and 3' ends mean on a DNA strand?

Answer 1

Well, as you know, DNA stands for deoxyribonucleic acid, and consists of phosphates, sugars, and bases. The deoxyribose sugar consists of 5 carbons and an oxygen in a ring, and the carbons can be numbered 5', 4', 3', 2', and 1'. Why the "prime"? The prime means you are talking about the carbons in the deoxyribose RING, and not the carbons of the base; it is just a naming convention. When individual nucleotides link up to make DNA polymers, it is the 3' hydroxyl (OH) that links up with the 5' phosphate group to form what is known as a phosphodiester bond.