Question

Can a DNA strand bind to a complementary RNA strand? Explain.

Short answer

Yes, a DNA strand can bind to a complementary RNA strand through a process called hybridization, forming a DNA-RNA hybrid duplex. This interaction occurs due to base-pairing rules in nucleic acids and is energetically favorable as a result of hydrogen bonding between the complementary bases.

Step-by-step solution

Understanding DNA and RNA Structures

DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are both nucleic acids, which are polymers made of nucleotide monomers. The main difference between DNA and RNA is the sugar component in their nucleotide monomers: DNA has a deoxyribose sugar, while RNA has a ribose sugar. Furthermore, DNA usually forms a double helix structure while RNA is usually single-stranded. In terms of bases, DNA has adenine (A), thymine (T), guanine (G), and cytosine (C), while RNA has adenine (A), uracil (U), guanine (G), and cytosine (C).

Base Pairing

The bases in DNA and RNA can form hydrogen bonds with each other. In DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C) through Watson-Crick base-pairing rules. In RNA, instead of thymine (T), there is uracil (U), so adenine (A) pairs with uracil (U) and guanine (G) pairs with cytosine (C). These base-pairing rules are crucial for the interaction between DNA and RNA, as they allow for complementary pairing.

DNA-RNA Hybridization

When a single-stranded DNA is exposed to a complementary RNA, the bases on each strand can form hydrogen bonds with each other, creating a DNA-RNA hybrid duplex. This process is called hybridization and occurs because the interaction between complementary bases on different strands is energetically favorable. The DNA-RNA hybrid duplex typically forms an A-form helix structure, different from the B-form helix present in the DNA double helix.

Conclusion

Yes, a DNA strand can bind to a complementary RNA strand through the process of hybridization, forming a DNA-RNA hybrid duplex. This interaction is governed by the base-pairing rules in nucleic acids and is energetically favorable due to hydrogen bonding between the complementary bases.

Key concepts

Base Pairing

Base pairing is a fundamental principle of nucleic acid interaction, allowing specific pairs of nitrogenous bases to form stable hydrogen bonds. In the world of genetics, this pairing is immensely important as it secures the structure of DNA and RNA molecules, enabling them to carry genetic information.
The rules of base pairing emerge from molecular structures:

• In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
• In RNA, adenine (A) pairs with uracil (U) since RNA lacks thymine, while guanine (G) continues to pair with cytosine (C).

These pairs are often referred to as complementary bases. The sequence of one strand determines the sequence of its pair through these base-pairing rules. During processes such as DNA replication and transcription, base pairing enables the synthesis of new strands by guiding the selection of complementary nucleotides.
Additionally, the ability to form RNA-DNA hybrids becomes possible through base pairing, facilitating various biological processes.

Nucleic Acid Structure

Nucleic acid structure is defined by its sequence of nucleotides, each consisting of a sugar, a phosphate, and a nitrogenous base. This structure forms the backbone of DNA and RNA, two crucial molecules in cellular function and genetic encoding.
DNA, or deoxyribonucleic acid, generally exists as a double helix. This helicoidal structure arises from the sugar-phosphate backbone twisting around a central axis with complementary base pairs located in the middle. RNA, or ribonucleic acid, differs primarily as it is usually single-stranded, often folding into complex secondary structures.
A key distinction between DNA and RNA is the type of sugar present:

• DNA contains deoxyribose, leading to a more stable double-stranded helix, ideal for long-term genetic storage.
• RNA includes ribose, making the molecule more reactive and suitable for roles in synthesis and catalysis.

Additionally, DNA includes the base thymine, complementing adenine, while RNA uses uracil in its place, influencing how these molecules interact both internally and with each other.

Hydrogen Bonding

Hydrogen bonding plays a crucial role in the stability and properties of nucleic acids. These bonds form between hydrogen atoms covalently linked to electronegative atoms like nitrogen or oxygen, and another electronegative atom with a lone pair of electrons.
In the context of DNA and RNA, hydrogen bonds are responsible for holding together base pairs, ensuring the structural integrity of double-stranded regions whether they are part of DNA, RNA, or a DNA-RNA hybrid.
The specific pairs allowed in genetic material, namely A-T (or A-U) and G-C, are due to the optimal hydrogen bonding possible between these bases:

• Adenine and thymine (or uracil) form two hydrogen bonds.
• Guanine and cytosine form three hydrogen bonds, providing greater stability.

This hydrogen bonding influences the overall stability and melting temperature of nucleic acid structures. It is also the reason these molecules can undergo processes such as DNA replication, transcription, and hybridization. In hybrids of DNA and RNA, the A-form helix structure results from these interactions, reflecting the strengths and variances attributed to hydrogen bonding patterns.