Question

which three descriptions correctly describe the diagram of dna above? select the three best answers.
the part of one strand in dna on the left and the part of the second strand in dna on the right are actually identical—they are just mirror images of one another (meaning, their orientations are flipped).
the ring structures shown here contain nitrogen (n) atoms and some double bonds.
in the upper hydrogen bond shown here, the oxygen (o) involved is double - bonded to a carbon and has a partial negative charge because of its higher electronegativity. to the right, the hydrogen (h) atom involved has a partial positive charge because the more electronegative nitrogen (n) atom it is bonded to has pulled the shared electrons away from the hydrogen nucleus.
in the lower hydrogen bond shown here, the hydrogen (h) atom involved has a partial positive charge because the more electronegative nitrogen (n) atom it is bonded to has pulled the shared electrons away from the hydrogen nucleus. to the right, the nitrogen (n) involved is bonded to two carbon atoms and has a partial negative charge because of its higher electronegativity.

Explanation:

1. DNA strands are complementary, not identical mirror - images, so the first statement is false.
2. The ring structures in the DNA bases (as shown) contain nitrogen atoms and double - bonds, which is correct.
3. In a hydrogen bond between DNA bases, oxygen (double - bonded to carbon) has a partial negative charge due to its high electronegativity, and hydrogen bonded to nitrogen has a partial positive charge as nitrogen pulls shared electrons, which is correct.
4. Similarly, in the lower hydrogen bond, hydrogen bonded to nitrogen has a partial positive charge and nitrogen bonded to carbon has a partial negative charge due to electronegativity differences, which is correct.

Answer:

The ring structures shown here contain nitrogen (N) atoms and some double bonds.
In the upper hydrogen bond shown here, the oxygen (O) involved is double - bonded to a carbon and has a partial negative charge because of its higher electronegativity. To the right, the hydrogen (H) atom involved has a partial positive charge because the more electronegative nitrogen (N) atom it is bonded to has pulled the shared electrons away from the hydrogen nucleus.
In the lower hydrogen bond shown here, the hydrogen (H) atom involved has a partial positive charge because the more electronegative nitrogen (N) atom it is bonded to has pulled the shared electrons away from the hydrogen nucleus. To the right, the nitrogen (N) involved is bonded to two carbon atoms and has a partial negative charge because of its higher electronegativity.