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4. Definere major og minor groove i en DNA dobbelthelix
Stryer, s.748, fig.27.7; fig. 27.8
Devlin, s. 40
 

Double helical nucleic acid molecules contain two grooves between the sugar-phosphate backbones of the two helices, called the major and the minor groove. They are produced by the interwinding of the two strands.

The grooves arise because the glycosidic bonds between the bases and the backbone pentose are not arranged diametrically opposite to each other, but are displaced towards the minor groove.

Because of the non-simetrical glycosidic bonds, the nucleotide sequence of DNA can be detected by looking inside the grooves, without being necessary to dissociate the double helix.

Each base always displays the same atoms in the groove. This is very important, because a lot of transcription factors can recognize their DNA binding site by being able to scan the DNA sequence and recognize the specific atoms. It is usually the major groove that serves as a site for DNA-protein interaction.

In B-DNA, the major groove is wider (12Å vs. 6Å) and deeper (8.5Å vs. 7.5Å) in comparison to the minor groove.

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