Question

DNA forms secondary structure only when two DNA strands align in antiparallel-instead of parallel-fashion. Which statement best explains why?

a.Sugars on antiparallel strands can interact via hydrogen bonding; sugars on parallel strands cannot.
b.Only antiparallel strands have a primary structure, which is required to form secondary structure.
c.Phosphate groups on antiparallel strands can interact via hydrogen bonding; phosphate groups on parallel strands cannot.
d.Bases on antiparallel strands form G-C and A-T pairs via hydrogen bonding; bases on parallel strands do not

Answer 1

DNA strands align in an antiparallel fashion to D) allowing for complementary base pairing of A-T and C-G via hydrogen bonds, forming the stable double-helix structure.

Step-by-step explanation:

The reason why DNA forms its secondary structure only when two DNA strands align in an antiparallel fashion is best explained by option d: Bases on antiparallel strands form G-C and A-T pairs via hydrogen bonding; bases on parallel strands do not. The antiparallel nature of the strands, with the 3' end of one strand facing the 5' end of the other, allows for complementary base pairing, which is essential for the double-helix structure of DNA. Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G) through hydrogen bonds, with A and T forming two hydrogen bonds, while C and G form three, which stabilizes the DNA molecule.