DNA and RNA Structural Features: Grooves, Helices, and Base Pairing
What is a bulge/loop in RNA structure?
A region where bases do not pair within a stem, causing a bulge, which adds flexibility.
What is the shape of DNA's secondary structure?
A right-handed double helix (B-DNA).
What is a pseudoknot in RNA?
A structure where a loop pairs with a sequence outside its stem, creating complex tertiary interactions.
What is a hairpin (stem-loop) structure in RNA?
A structure where a single RNA strand folds back on itself, forming a double-stranded stem and a loop.
What distinguishes A-DNA from B-DNA?
A-DNA is a right-handed, shorter, and wider helix that forms under dehydrating conditions.
What type of helix do RNA duplexes adopt?
A-form helix, not B-form.
What is the width of the minor groove in DNA?
About 12 Å wide.
What is the width of the major groove in DNA?
About 22 Å (angstroms) wide.
What base pairs with Uracil in RNA?
Adenine (A) pairs with Uracil (U) using 2 hydrogen bonds.
What are the four bases found in RNA?
Adenine (A), Uracil (U), Guanine (G), and Cytosine (C).
What are the common secondary structures formed by RNA?
Hairpins, loops, and double-stranded regions that adopt an A-form helix.
What is the role of hydrogen bonding in DNA structure?
Hydrogen bonding stabilizes the base pairs, contributing to the overall stability of the DNA double helix.
What stabilizes the DNA double helix structure?
Hydrogen bonds between base pairs and base stacking interactions.
What stabilizes the hairpin structure in RNA?
Intramolecular hydrogen bonds between complementary bases and base stacking in the stem.
What is the primary function of the minor groove?
It contains less distinct patterns of atoms and is involved in structural stability and nonspecific DNA binding.
What is the primary function of the major groove?
It exposes distinct patterns of hydrogen bond donors and acceptors, allowing proteins to read the DNA sequence without unwinding the helix.
What is the typical structure of B-DNA?
It has antiparallel strands forming a right-handed helix with 10 base pairs per turn.
What is the significance of the right-handed helix in B-DNA?
It is the most common form of DNA, crucial for its biological functions.
What distinguishes Z-DNA from B-DNA?
Z-DNA is a left-handed helix with a zigzag sugar-phosphate backbone, often rich in GC sequences.
What is the structural feature of DNA that contributes to its stability?
Base stacking via van der Waals forces and hydrophobic interactions.
Which types of molecules typically bind to the minor groove?
Certain DNA-binding drugs and histones, especially in A-T rich regions.
What is a quick summary of DNA secondary structure?
DNA consists of two antiparallel strands forming a double helix stabilized by hydrogen bonds and base stacking.
What is the stability difference between RNA and DNA?
DNA is chemically stable, while RNA is less stable due to the 2′-OH group promoting hydrolysis.
Which types of molecules typically bind to the major groove?
DNA-binding proteins such as transcription factors and enzymes.
What type of bonds connect the sugar and phosphate in RNA and DNA?
Phosphodiester bonds.
What are the key chemical differences between RNA and DNA?
RNA has ribose sugar and uracil instead of thymine, while DNA has deoxyribose and thymine.
What is a quick summary of RNA secondary structure?
RNA is usually single-stranded and folds into structures like hairpins and loops through intramolecular base pairing.
What is the primary structural difference between RNA and DNA?
RNA is usually single-stranded and folds upon itself, while DNA is double-stranded forming a stable double helix.
What type of sugar is found in RNA?
Ribose, which has a 2′-OH group, making RNA more reactive and flexible.
How does the pitch of the helix relate to DNA structure?
The helix pitch is the distance per full turn, approximately 3.4 nm in B-DNA.
How do the major and minor grooves differ in terms of information content?
The major groove has high information content, allowing for easy distinction of base pairs, while the minor groove has low information content.
What causes the formation of major and minor grooves in DNA?
The uneven attachment of bases to the sugar-phosphate backbone as the two antiparallel strands twist around each other.
How do the strands of DNA orient in relation to each other?
They are antiparallel, with one strand running 5′ to 3′ and the other 3′ to 5′.
What is the significance of major and minor grooves in DNA?
They are regions where proteins can bind to the DNA.
What is the role of hydrogen bonds in RNA secondary structure?
They form between base pairs (A-U, G-C, G-U) to stabilize the folded structure.
How many hydrogen bonds are formed between Guanine and Cytosine?
Three hydrogen bonds.
