Nucleic acids Flashcards
What are the main types of RNA?
mRNA (messenger RNA): Carries genetic information from DNA to ribosomes.
tRNA (transfer RNA): Brings amino acids to the ribosome during translation.
rRNA (ribosomal RNA): Structural and functional component of ribosomes.
What is the structural difference between RNA and DNA?
RNA contains ribose sugar; DNA contains deoxyribose.
RNA uses uracil (U) instead of thymine (T).
What is the secondary structure of RNA?
Single-stranded but can fold into complex shapes, forming hairpins, loops, and bulges due to intramolecular base pairing.
What roles do non-coding RNAs play?
Regulate gene expression (e.g., miRNA, siRNA).
Catalyse reactions (e.g., ribozymes).
What is the function of ribozymes?
RNA molecules with enzymatic activity, such as self-splicing introns and the peptidyl transferase activity of the ribosome.
What is the structure of DNA?
Double helix with antiparallel strands.
Sugar-phosphate backbone and nitrogenous bases (adenine, thymine, cytosine, guanine) pair via hydrogen bonds.
What are Chargaff’s rules?
A pairs with T via 2 hydrogen bonds; C pairs with G via 3 hydrogen bonds.
The amount of A equals T, and C equals G.
What is the difference between A-DNA, B-DNA, and Z-DNA?
B-DNA: Right-handed, most common form in cells.
A-DNA: Right-handed, shorter and more compact, formed under dehydrating conditions.
Z-DNA: Left-handed, occurs in regions of high GC content.
What is the role of the major and minor grooves in DNA?
Provide binding sites for proteins and enzymes.
The major groove offers more access to base pairs for specific interactions.
What stabilizes the DNA double helix?
Hydrogen bonding between bases.
Base stacking interactions (hydrophobic).
Ionic interactions with phosphate groups.
What is the mechanism of DNA replication?
Semi-conservative: Each new DNA molecule has one parental and one newly synthesized strand.
What enzymes are involved in DNA replication?
Helicase: Unwinds the DNA helix.
Primase: Synthesizes RNA primers.
DNA Polymerase: Adds nucleotides to the growing strand.
Ligase: Joins Okazaki fragments on the lagging strand.
Topoisomerase: Relieves supercoiling ahead of the replication fork.
What are Okazaki fragments?
Short DNA segments synthesized discontinuously on the lagging strand.
How is replication initiated?
Begins at origins of replication.
Replication forks form and proceed bidirectionally.
What ensures fidelity in DNA replication?
Proofreading by DNA polymerase.
Mismatch repair mechanisms post-replication.
What is the role of telomerase in replication?
Extends telomeres (ends of chromosomes) in eukaryotic cells to prevent loss of genetic material.
