Florida Biology EOC Practice Test

What type of bonding forms between the nitrogenous bases of each DNA strand, providing just enough attraction to hold the two strands together?

1. Covalent bonding

2. Hydrogen bonding

3. Ionic bonding

4. Metallic bonding

The correct answer is: Covalent bonding

The type of bonding that forms between the nitrogenous bases of each DNA strand is hydrogen bonding. This type of bond is characterized by the attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom. In DNA, the complementary nitrogenous bases (adenine pairs with thymine, and cytosine pairs with guanine) are held together by hydrogen bonds, which are relatively weak compared to covalent bonds. This weak attraction is crucial because it allows the two strands of DNA to separate easily during processes like DNA replication and transcription, making the genetic information accessible for use by the cell. Covalent bonds, while strong and essential for forming the backbone of the DNA molecule (linking sugar and phosphate groups), do not specifically account for the pairing of nitrogenous bases across the two strands. Ionic bonding involves the transfer of electrons and the attraction between charged ions, which is not applicable to the interactions between DNA bases. Metallic bonding pertains to the properties of metals and does not apply in this context. Thus, hydrogen bonding provides the correct level of attraction needed to hold the strands together while allowing them to separate when necessary, making it the most suitable type of bonding for DNA’s structure and function.