In which direction are DNA strands read?

DNA strands are read in the 5 to 3 direction during processes such as replication and transcription. This convention is based on the orientation of the sugar-phosphate backbone of the DNA molecule. The numbering of the carbon atoms in the sugar rings (deoxyribose in DNA) identifies the 5' and 3' ends. The 5' end has a phosphate group attached to the fifth carbon, while the 3' end has a hydroxyl group attached to the third carbon. When DNA or RNA polymerases synthesize a new strand, they add nucleotides to the 3' end of the growing chain, effectively reading the template strand in the 3' to 5' direction, which allows for the assembly of the new strand in the 5' to 3' direction. This orientation is crucial for the enzyme's activity and for maintaining the integrity of the genetic code.

The other potential directions, such as circular reading or left to right, do not describe the established biochemical processes regarding the reading of DNA strands. DNA is a linear molecule in terms of strands being read, and while it can exist in a circular form (as in plasmids or certain viral genomes), the reading direction during synthesis is still