Question

Discuss ss vs. ds DNA: the direction of strands, the ends of strands (OH vs. phosphate), and give an example of ds 5-base long piece of DNA.

Give detailed epxlanation

Answer 1

DNA is usually a double-helix and has two strands running in opposite directions. Each chain is a polymer of subunits called nucleotides.
Each strand has a backbone made up of (deoxy-ribose) sugar molecules linked together by phosphate groups. The 3' C of a sugar molecule is connected through a phosphate group to the 5' C of the next sugar. This linkage is also called 3'-5' phosphodiester linkage. All DNA strands are read from the 5' to the 3' end where the 5' end terminates in a phosphate group and the 3' end terminates in a sugar molecule.