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K 2 Cr 2 O 7 (aq) + 2 KOH → 2 K 2 CrO 4 + H 2 O. Or, the fusion of potassium hydroxide and chromium trioxide: 2 KOH + CrO 3 → K 2 CrO 4 + H 2 O. In solution, the behavior of potassium and sodium dichromates are very similar. When treated with lead(II) nitrate, it gives an orange-yellow precipitate, lead(II) chromate.
The DNA model shown (far right) is a space-filling, or CPK, model of the DNA double helix. Animated molecular models, such as the wire, or skeletal, type shown at the top of this article, allow one to visually explore the three-dimensional (3D) structure of DNA. Another type of DNA model is the space-filling, or CPK, model.
Nucleic acid design is central to the fields of DNA nanotechnology and DNA computing. [2] It is necessary because there are many possible sequences of nucleic acid strands that will fold into a given secondary structure, but many of these sequences will have undesired additional interactions which must be avoided.
DNA exists in many possible conformations that include A-DNA, B-DNA, and Z-DNA forms, although only B-DNA and Z-DNA have been directly observed in functional organisms. [14] The conformation that DNA adopts depends on the hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and ...
Under torsional stress, a Z-DNA structure can form with opposite twist to B-form DNA, but this is rare within the cellular environment. [24] The discovery of topoisomerases and gyrases , enzymes that can change the linking number of circular nucleic acids and thus "unwind" and "rewind" the replicating bacterial chromosome, solved the ...
In early 1953, Pauling published a triple helix model of DNA, which subsequently turned out to be incorrect. [3] Both Crick, and particularly Watson, thought that they were racing against Pauling to discover the structure of DNA. Max Delbrück was a physicist who recognized some of the biological implications of quantum physics.
The solenoid structure's most obvious function is to help package the DNA so that it is small enough to fit into the nucleus. This is a big task as the nucleus of a mammalian cell has a diameter of approximately 6 μm, whilst the DNA in one human cell would stretch to just over 2 metres long if it were unwound. [6]