Why is the double helical shape of DNA advantageous?

The double helical shape of DNA is held together by covalent bonds on the outer bands (phosphate groups and deoxyribose) and the nitrogen bases in the middle are held together by hydrogen bonds. The covalent bonds are strong and serve for stability while the hydrogen bonds are weak individually (can be split individually by helicase for replication) However, many hydrogen bonds together can be very strong and can help protect the precious genetic code from being damaged by outer disturbances. The helical shape helps provide stability yet flexibility in times of replication or transcription. DNA is also an extremely long molecule that need to be compacted in order to fit in a localized region on the cell (nucleus). Its shape allows it to be easily folded and compacted around histones and further folded in on itself when the cell is in interphase and manipulated into dense chromosomes for mitosis.

The double helix structure makes the DNA molecule more stable as it is held together by hydrogen bonds.