If a DNA molecule was transferred from biological buffer to a low humi...
On reducing the humidity below 50% the naturally occurring B-DNA has propensity to form A DNA conformation. B-DNA needs around 30% water by weight, to maintain its native conformation in the crystalline state. Partial dehydration converts B DNA to A-DNA (A DNA has a shallow, wide minor groove and a narrow, deeper major groove). The transition for this transformation occurs at about 20 water molecules per base pair, with its midpoint at about 15 water molecules per base pair (at about 85% relative humidity). The B-DNA possesses a spanning water network, and it is the loss of its continuity together with the competition between hydration and direct cation coupling to the free oxygen atoms in the phosphate groups that give rise to the transition to A-DNA. This dehydration induced structural transition decreases the free energy required for A-DNA deformation and twisting, which is usefully employed by encouraging supercoiling but eventually leads to denaturation. Further dehydration results in the least hydrated D-DNA (favored by excess counter-ions that shield the DNA phosphate charges), which has a very narrow minor groove with a string of alternating water and counter-ions distributed along its edge
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If a DNA molecule was transferred from biological buffer to a low humi...
Introduction:
DNA is a double-stranded helical molecule that carries genetic information. It can exist in different conformations, such as A-DNA, B-DNA, and Z-DNA, depending on the environmental conditions.
Explanation:
When a DNA molecule is transferred from a biological buffer to a low humidity condition (less than 50% humidity), the most likely transition in the biomolecule would be B-DNA to A-DNA. This is because:
1. B-DNA is the most stable and common conformation of DNA under physiological conditions, which means it requires a certain level of humidity to maintain its structure.
2. A-DNA is a more compact and compressed form of DNA than B-DNA, which is better suited for low humidity conditions. It has a shorter and wider helix, with base pairs tilted by 20 degrees from the helix axis.
3. Z-DNA is a left-handed helix that is more stable under high salt and temperature conditions, and it is unlikely to form under low humidity conditions.
Conclusion:
In summary, the transition from B-DNA to A-DNA is the most likely in a low humidity condition, as A-DNA is a more compact and stable form of DNA under such conditions.