Animation of the structure of a section of DNA. The rules are horizontally between the two spiraling strands. Extended version double helix: a) Righthanded, b) double helix is a right-handed spiral that is, each nucleotide chains right turn, this can be verified if you look, going from bottom to top, in the direction the segments are the threads that are in the foreground. If the two strands rotate clockwise it is said that the double helix is right-handed, and if they turn to left, left-handed (this form may appear in helices alternatives because conformational changes in DNA).But the most common conformation adopted by the DNA double helix is right-handed, turning every couple of bases on the previous approximately 36 . When the two DNA strands are rolled over each other (either left or right) , holes or cracks are formed between a thread and the other, exposing the sides of the nitrogenous bases inside (see animation). In the most common conformation DNA adopts appear, because of the angles formed between sugars of both strands of each pair of nitrogenous bases, two types of cracks around the surface of the double helix: one, the cleft or major groove, which is 22 (2.2 nm) wide, and the other, the groove or minor groove, which is 12 (1.2 nm) wide. Every turn of helix, when it has made a 360 or what is the same from beginning to end slit slit couple minor measure by both 34th, and in each of these rounds is about 10.5 bp.Major and minor grooves of the double helix. The width of the slit greater implies that the ends of the bases are more accessible in this, so that the amount of exposed chemical groups is also greater which makes the differentiation between the base pairs AT, TA, CG, GC. As a result, will also be easier to accept DNA sequences from different proteins without the need to open the double helix. Thus, proteins like transcription factors that bind to specific sequences, frequent contact with the sides of the bases exposed in the groove more. By contrast, the chemical groups that are exposed in the minor groove are similar, so that the recognition of base pairs is more difficult, for it is said that the couple split contains more information than the lower groove.