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| Name | Different Forms of DNA |
| Video Uploader | Video From biotech simplified |
| Upload Date | This Video Uploaded At 19-04-2020 08:43:20 |
| Video Discription | Three major forms of DNA are double stranded and connected by interactions between complementary base pairs. These are terms A-form, B-form,and Z-form DNA. B-form DNA The information from the base composition of DNA, the knowledge of dinucleotide structure, and the insight that the X‑ray crystallography suggested a helical periodicity were combined by Watson and Crick in 1953 in their proposed model for a double helical structure for DNA. They proposed two strands of DNA -- each in a right‑hand helix -- wound around the same axis. The two strands are held together by H‑bonding between the bases Z-form DNA Z-DNA is a radically different duplex structure, with the two strands coiling in left-handed helices and a pronounced zig-zag (hence the name) pattern in the phosphodiester backbone. Z-DNA can form when the DNA is in an alternating purine-pyrimidine sequence such as GCGCGC, and indeed the G and C nucleotides are in different conformations, leading to the zig-zag pattern. The big difference is at the G nucleotide. It has the sugar in the C3' endoconformation (like A-form nucleic acid, and in contrast to B-form DNA) and the guanine base is in the synconformation. This places the guanine back over the sugar ring, in contrast to the usual anticonformation seen in A- and B-form nucleic acid. Note that having the base in the anticonformation places it in the position where it can readily form H-bonds with the complementary base on the opposite strand. The duplex in Z-DNA has to accomodate the distortion of this G nucleotide in the synconformation. The cytosine in the adjacent nucleotide of Z-DNA is in the "normal" C2' endo, anticonformation. A-form DNA A-DNA is a right-handed double helix made up of deoxyribonucleotides. It appears when the relative humidity of the environment is less than 75%, which means that it is rarely present in normal physiological condition. The two strands of A-DNA are anti-parallel with each other and not symmetrical. The molecule is asymmetrical is because the glycosidic bonds of a base pair are not diametrically opposite to each other. Therefore, major grooves and minor grooves can be observed in each turn. One turn of the helix consists of 11 base pairs with a length of 2.86nm. The backbone of A-DNA is formed by sugar phosphates that are linked continuous using phosphodiester bonds. All the nitrogenous bases are at the core centre of the helix. Hydrogen bonds between nitrogenous bases allow the molecule to exhibit the double helix structure. |
| Category | Education |
| Tags | A DNA B DNA AND Z DNA | DIFFERENT FORMS OF DNA | FORMS OF DNA | RARE FORMS OF DNA | WHY DIFFERENT FORMS OF DNA EXISTS | B DNA | Z DNA | A DNA | E DNA | C DNA | D DNA |
