MCQs

Ribosomal RNA forms the dense, intricately folded catalytic and structural core of both the large and small ribosomal subunits.

Prokaryotes handle all transcription with a single multi-subunit core RNA polymerase that relies on changeable sigma factors for promoter recognition.

miRNAs are tiny, non-coding RNA molecules that associate with RISC complexes to pair with matching mRNAs and suppress translation.

The AAUAAA consensus sequence is recognized by specific endonucleases that cleave the nascent RNA transcript before poly-A polymerase adds the tail.

The coding (sense) DNA strand matches the mRNA transcript sequence exactly, with the sole exception that thymine (T) is replaced by uracil (U).

The T$psi$C loop contains ribothymidine and pseudouridine, which are critical for anchoring the tRNA molecule to the large ribosomal subunit.

Accurate translation relies entirely on the precise hydrogen-bond pairing between three consecutive mRNA bases and three complementary tRNA bases.

In mammals and high eukaryotes, a single large 45S pre-rRNA transcript is synthesized and then cleaved to produce the 18S, 5.8S, and 28S rRNAs.

The transcription bubble is the localized region of single-stranded DNA where RNA polymerase matches incoming ribonucleotides to the template.

Being single-stranded without a permanent complementary partner allows mRNA to remain dynamic and easily accessible to ribosomes.

Transcription initiation begins with a nucleoside triphosphate without clearing the pyrophosphate, leaving a 5'-triphosphate terminal.

Rho factor is an ATP-dependent helicase that tracks along the growing RNA transcript to unwind the RNA-DNA hybrid and terminate transcription.

A nonsense mutation converts an amino acid-specifying codon into a termination codon (UAA, UAG, or UGA), shortening the final protein.

Alpha-amanitin, a toxin from the death cap mushroom, is a highly specific inhibitor of eukaryotic RNA Polymerase II.

RNA viruses possessing RNA-dependent RNA polymerase can replicate their RNA directly from an RNA template without creating a DNA intermediate.

The 23S rRNA located in the large (50S) prokaryotic ribosomal subunit acts as the peptidyl transferase ribozyme.

The chemical reactivity of the 2'-OH group allows RNA to participate in catalytic mechanisms, giving rise to ribozymes.

Transcription produces an RNA strand complementary and anti-parallel to the DNA template strand, replacing thymine with uracil.

Nucleic acid strands align anti-parallelly; therefore, the 5'-AUG-3' codon pairs with the 3'-UAC-5' (or 5'-CAU-3') anticodon.