Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

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Study for the Biology STAAR Test. Improve your skills with flashcards and multiple choice questions, each question is accompanied by hints and explanations. Prepare for success!

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What type of bond holds the base pairs of DNA together?

Covalent bonds
Ionic bonds
Hydrogen bonds
Metallic bonds

The correct answer is: Hydrogen bonds

The base pairs of DNA are held together by hydrogen bonds, which are a type of weak, non-covalent interaction that occurs between a hydrogen atom, which is covalently bonded to an electronegative atom (like nitrogen or oxygen), and another electronegative atom. In the context of DNA, these hydrogen bonds form between complementary nitrogenous bases—adenine with thymine and guanine with cytosine. This specific bonding is crucial for the stability of the DNA helix, as it allows for the two strands of DNA to separate during processes such as replication and transcription without requiring excessive energy to break the bonds. The weak nature of hydrogen bonds is what facilitates these separations, allowing the DNA to open up when needed for biological processes, while still keeping the overall structure stable when the strands are together. Covalent bonds, in comparison, are much stronger and are responsible for holding the sugar-phosphate backbone of each DNA strand together. Ionic bonds and metallic bonds do not play a significant role in the structural integrity of DNA base pairing. Hence, the role of hydrogen bonds is essential for the base pairing mechanism that underpins the functionality of DNA.