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Like the more common B-DNA, A-DNA is a right-handed double helix with major and minor grooves. However, as shown in the comparison table below, there is a slight increase in the number of base pairs (bp) per turn. This results in a smaller twist angle, and smaller rise per base pair, so that A-DNA is 20-25% shorter than B-DNA.
B-DNA base pairs are nearly perpendicular to the helix axis. The sugar pucker which determines the shape of the a-helix, whether the helix will exist in the A-form or in the B-form, occurs at the C2'-endo. [13] A-DNA, is a form of the DNA duplex observed under dehydrating conditions. It is shorter and wider than B-DNA. RNA adopts this double ...
At least three DNA conformations are believed to be found in nature, A-DNA, B-DNA, and Z-DNA. The B form described by James Watson and Francis Crick is believed to predominate in cells. [27] It is 23.7 Å wide and extends 34 Å per 10 bp of sequence. The double helix makes one complete turn about its axis every 10.4–10.5 base pairs in solution.
Given the difference in widths of the major groove and minor groove, many proteins which bind to DNA do so through the wider major groove. [6] Many double-helical forms are possible; for DNA the three biologically relevant forms are A-DNA, B-DNA, and Z-DNA, while RNA double helices have structures similar to the A form of DNA.
DNA and RNA also contain other (non-primary) bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m 5 C). In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ψ), dihydrouridine (D), inosine (I), and 7-methylguanosine ...
One major difference between DNA and RNA is the sugar, with the 2-deoxyribose in DNA being replaced by the related pentose sugar ribose in RNA. [12] A section of DNA. The bases lie horizontally between the two spiraling strands [15] (animated version).
When it comes to insects' DNA, humans have a bit less in common. For example, fruit flies share 61 percent of disease-causing genes with humans, which was important when NASA studied the bugs to ...
Nucleic acid types differ in the structure of the sugar in their nucleotides–DNA contains 2'-deoxyribose while RNA contains ribose (where the only difference is the presence of a hydroxyl group). Also, the nucleobases found in the two nucleic acid types are different: adenine , cytosine , and guanine are found in both RNA and DNA, while ...