What is meant by the 3' and 5' end?

The 3' and 5' ends refer to the orientation of a DNA or RNA strand, indicating the direction in which the nucleotides are arranged. The 5' end has a phosphate group attached to the fifth carbon of the sugar molecule, while the 3' end has a hydroxyl (-OH) group on the third carbon. This directional terminology is crucial for processes like DNA replication and transcription, as nucleic acids are synthesized in the 5' to 3' direction.