Which type of chemical bond holds together the nitrogen bases in DNA?

• A. Ionic bond
• B. Hydrogen bond
• C. Metallic bond
• D. Covalent bond

Answer: (B)

Verified step by step guidance

1. Understand the types of chemical bonds: Ionic bonds involve the transfer of electrons between atoms, covalent bonds involve sharing of electrons, metallic bonds involve a 'sea' of delocalized electrons, and hydrogen bonds are weak attractions between a hydrogen atom bonded to an electronegative atom and another electronegative atom.
2. Recall the structure of DNA: DNA consists of a sugar-phosphate backbone connected by covalent bonds, and nitrogenous bases that pair with each other across the two strands.
3. Identify the bond between nitrogen bases: The nitrogen bases (adenine, thymine, cytosine, guanine) pair through specific interactions that are not covalent or ionic but involve weaker attractions.
4. Recognize that these interactions are hydrogen bonds: Hydrogen bonds form between complementary nitrogen bases (A with T, and C with G) and are responsible for holding the two strands of DNA together.
5. Conclude that the correct type of bond holding the nitrogen bases together in DNA is the hydrogen bond.