Àwọn atínrín alọ́po méjéèjì náà dá igbáẹ̀yìn DNA. Alọ́po ẹ̀mẹjì míràn kan náà tún ṣe é rí nípa títẹ̀lé àwọn àyè, tàbi àwọn ibitooro, tó wà láàrin àwọn atínrín náà. Àwọn àyè yìí wà nítòsí sí àwọn ìpìlẹ̀ méjì ó sìl lè pèsè [[binding site|ojú ìdè]]. AsNítorípé theàwọn strandsatínrín arekò notwà directlyníwájú oppositeara each otherwọn, theàwọn groovesibitooro arelò unequallyní sizedìtóbi dídọ́gba. OneIbitooro groovekan, theibitooro major grooveàgbà, isjẹ́ 22 Å widení andfífẹ̀, the otherèkejì, theibitooro minor groovekékeré, isjẹ́ 12 Å widení fífẹ̀.<ref>{{cite journal |author=Wing R, Drew H, Takano T, Broka C, Tanaka S, Itakura K, Dickerson R |title=Crystal structure analysis of a complete turn of B-DNA |journal=Nature |volume=287 |issue=5784 |pages=755–8 |year=1980 |pmid=7432492 |doi=10.1038/287755a0|bibcode = 1980Natur.287..755W }}</ref> The narrowness of the minor groove means that the edges of the bases are more accessible in the major groove. As a result, proteins like [[transcription factor]]s that can bind to specific sequences in double-stranded DNA usually make contacts to the sides of the bases exposed in the major groove.<ref name="Pabo1984">{{cite journal |author=Pabo C, Sauer R |title=Protein-DNA recognition |journal=Annu Rev Biochem |volume=53 |pages=293–321 |year=1984 |pmid=6236744 | doi = 10.1146/annurev.bi.53.070184.001453}}</ref> This situation varies in unusual conformations of DNA within the cell ''(see below)'', but the major and minor grooves are always named to reflect the differences in size that would be seen if the DNA is twisted back into the ordinary B form.
