Which of the following statements about the DNA double helix is TRUE?
Multiple Choice
Complementary base pairing across the double helix allows information to be transferred via DNA replication.
Complementary base pairing allows the production of a DNA strand that is identical to its template strand (or parts of the template strand) ?via DNA replication.
It takes large amounts of energy to separate the double helix because it is held together via covalent bonds.
The 3′ ?end of the double helix terminates in a nitrogenous base on the 3′ ?carbon.
The 5′ ?end of the double helix terminates in a nitrogenous base on the 5′ ?carbon.
The Correct Answer and Explanation is :
The correct statement is:
Complementary base pairing allows the production of a DNA strand that is identical to its template strand (or parts of the template strand) via DNA replication.
Explanation:
- Complementary Base Pairing in DNA Replication: The DNA double helix consists of two strands that are complementary to each other. This means that adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). During DNA replication, the two strands of the helix are separated, and each strand serves as a template for the formation of a new complementary strand. DNA polymerase reads the template strand and adds nucleotides that are complementary to the exposed bases on the template strand, producing a new strand that is identical to the original strand (except for the newly synthesized strand being in the opposite direction). This mechanism ensures accurate replication of genetic information.
- Energy Required to Separate the Double Helix: DNA is held together by hydrogen bonds between complementary base pairs (A-T and C-G), not covalent bonds. Hydrogen bonds are weaker than covalent bonds, and thus, separating the strands requires less energy. The statement that DNA is held together via covalent bonds is incorrect in this context because covalent bonds are present in the backbone (between sugar and phosphate groups), but the pairing of bases is held together by hydrogen bonds.
- 3′ and 5′ Ends: The 3′ and 5′ ends refer to the carbon numbering in the sugar molecule of the nucleotides. The 3′ end has a hydroxyl group (-OH) attached to the third carbon of the sugar, while the 5′ end has a phosphate group attached to the fifth carbon. The statements suggesting that these ends terminate in nitrogenous bases are incorrect because the bases are part of the nucleotide structure, and the ends refer specifically to the orientation of the sugar-phosphate backbone.
In summary, the correct answer involves complementary base pairing, which plays a crucial role in ensuring that the new DNA strand is an accurate copy of the template during replication.