Which type of bonds hold the two strands of DNA together between complementary base pairs?

Which type of bonds hold the two strands of DNA together between complementary base pairs?

• A. Hydrogen bonds between complementary bases
• B. Covalent bonds within a nucleotide
• C. Ionic bonds between phosphate groups
• D. Metallic bonds in the DNA backbone

Answer: (A)

The two DNA strands are held together by hydrogen bonds formed between complementary bases on opposite strands. These hydrogen bonds are enough to keep the strands paired yet allow them to separate when DNA is replicated or transcribed. Adenine pairs with thymine using two hydrogen bonds, while guanine pairs with cytosine using three hydrogen bonds, which also helps explain why GC-rich regions are a bit more stable. The backbone of each strand is made up of covalent phosphodiester bonds linking sugar and phosphate units; these bonds hold each strand together but do not connect the two strands to each other. Ionic bonds between phosphate groups aren’t the main force keeping the strands together, and metallic bonds aren’t present in DNA. So the key interaction between the strands is hydrogen bonding between complementary bases.

The two DNA strands are held together by hydrogen bonds formed between complementary bases on opposite strands. These hydrogen bonds are enough to keep the strands paired yet allow them to separate when DNA is replicated or transcribed. Adenine pairs with thymine using two hydrogen bonds, while guanine pairs with cytosine using three hydrogen bonds, which also helps explain why GC-rich regions are a bit more stable.

The backbone of each strand is made up of covalent phosphodiester bonds linking sugar and phosphate units; these bonds hold each strand together but do not connect the two strands to each other. Ionic bonds between phosphate groups aren’t the main force keeping the strands together, and metallic bonds aren’t present in DNA. So the key interaction between the strands is hydrogen bonding between complementary bases.