Question

Compare the degree of hydrogen bonding in the base pair A-T found in DNA with that in the base pair \(\mathrm{A}-\mathrm{U}\) found in \(\overline{\mathrm{RNA}}\).

Short answer

Question: Compare the degree of hydrogen bonding between A-T base pair in DNA and A-U base pair in RNA. Answer: The degree of hydrogen bonding between A-T base pair in DNA and A-U base pair in RNA is the same, as both base pairs form 2 hydrogen bonds between them. However, the overall stability of DNA and RNA molecules depends on various factors, not just hydrogen bonding.

Step-by-step solution

Understand the Base Pairing in DNA and RNA

In DNA, adenine (A) pairs with thymine (T) through hydrogen bonding. In RNA, adenine (A) pairs with uracil (U) instead. These hydrogen bonds between complementary bases are responsible for holding the two strands of DNA or RNA together.

Examine the Hydrogen Bonds in Adenine-Thymine Pair

In the A-T base pair, adenine and thymine form 2 hydrogen bonds. Specifically, the nitrogen atom on adenine bonds with a hydrogen atom attached to an oxygen atom on thymine, and the nitrogen atom on thymine bonds with a hydrogen atom attached to a nitrogen atom on adenine.

Examine the Hydrogen Bonds in Adenine-Uracil Pair

In the A-U base pair, adenine and uracil also form 2 hydrogen bonds. Here, the hydrogen bond pattern is similar to that in the A-T pair, with the nitrogen atom on adenine bonding with a hydrogen atom attached to an oxygen atom on uracil, and the nitrogen atom on uracil bonding with a hydrogen atom attached to a nitrogen atom on adenine.

Compare the Degree of Hydrogen Bonding

Both A-T and A-U base pairs form 2 hydrogen bonds between them. Thus, the degree of hydrogen bonding is the same for both base pairs. However, it is important to note that the overall stability of DNA and RNA molecules depends on various factors, such as the surrounding environment and presence of other molecular interactions, not just hydrogen bonding.

Key concepts

Base Pairing in DNA

Base pairing is a crucial characteristic of DNA structure that ensures the accurate copying of genetic information during cellular replication processes. Throughout evolution, the highly specific interactions between nucleotide bases have contributed to the faithful transmission of genetic traits from one generation to the next.

In DNA, adenine (A) pairs with thymine (T) through two hydrogen bonds. This specific pairing, resulting from the optimal distance and orientation for hydrogen bonding between the two bases, allows for a consistent and stable double helical structure. The complementarity of the A-T pairing is what enables DNA to form the famous Watson-Crick model, ensuring that each strand can serve as a template for the creation of a new complementary strand.

Adenine-Thymine Hydrogen Bonds

The pairing between adenine and thymine in DNA is characterized by two hydrogen bonds that are critical for the molecule's stability and function. These bonds occur between specific atoms: one between the nitrogen atom of adenine and a hydrogen atom attached to an oxygen atom of thymine, and the other between the nitrogen atom on thymine and a hydrogen atom on adenine.

The precision of these interactions is not arbitrary; the geometry of the molecules is perfectly suited for this type of bonding, which influences the overall structure of DNA. The paired bases form the 'rungs' of the DNA 'ladder,' contributing to the double helix's twist and the molecule's ability to compact into the limited space of a cell nucleus.

Adenine-Uracil Hydrogen Bonds

In RNA, adenine pairs with uracil (U) instead of thymine. The adenine-uracil base pair also forms two hydrogen bonds, essential for maintaining the structural integrity of RNA molecules. Despite the chemical difference between thymine and uracil, the hydrogen bonding pattern remains similar, allowing A-U to maintain a stable base pair in the RNA structure.

This slight variation is significant in the overall DNA and RNA structure comparison; uracil lacks the methyl group found in thymine, which affects the overall spatial arrangement of the nucleic acid structure. This is an example of how a small chemical adjustment can influence the physical properties of a biomolecule.

DNA and RNA Structure Comparison

DNA Structure

DNA is typically found as a stable, double-stranded helix. The backbone of each strand is composed of alternating sugar (deoxyribose) and phosphate groups, with the sequence of bases protruding internally. In DNA, the presence of thymine contributes to its structural complexity and relative stability.

RNA Structure

RNA, however, often exists as a single-stranded molecule that can fold into various shapes due to its less rigid structure. RNA's sugar is ribose, which, like the presence of uracil instead of thymine, contributes to its vastly different properties compared to DNA, including its generally shorter lifespan within cells.

Molecular Stability of Nucleic Acids

The stability of nucleic acids like DNA and RNA is heavily influenced by hydrogen bonding between their bases. This hydrogen bonding, however, is not the only factor that determines the molecule's overall stability. Factors such as the helical structure, the presence of additional bonding interactions (like base stacking), and the cell's chemical environment all contribute to the nucleic acids' resilience.

For instance, the DNA double helix enjoys a higher stability due to the structure's ability to protect its hydrogen bonds, whereas RNA's structural versatility and reactive hydroxyl group in the ribose make it more prone to chemical interactions that can lead to breakdown. Despite the different stabilities, both DNA and RNA play essential roles in the flow of genetic information within biological systems.