Final answer:
In the B-form of DNA, the major groove is approximately 22 angstroms (2.2 nm) wide and facilitates important protein-DNA interactions.
Step-by-step explanation:
In the B-form of the double helical structure of DNA, which is the most common form found in biological systems, the major groove is typically wider than the minor groove. The major groove has a width of around 22 angstroms (2.2 nm) allowing for specific protein interactions. These grooves are essential for various biological processes, such as the binding of transcription factors during the transcription of DNA into RNA, and for the binding of other proteins that play a critical role in DNA replication and regulation.