MCQs

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.

A polysome (or polyribosome) consists of a single mRNA strand being translated simultaneously by several moving ribosomes to amplify protein yield.

snRNAs combine with specific proteins to form snRNPs ("snurps"), which build the spliceosome machinery responsible for removing introns.

A triplet code consisting of three consecutive nucleotides provides the minimum variations (43=64) needed to code for 20 amino acids.

Polycistronic mRNA is characteristic of prokaryotes, where a single promoter controls an operon containing multiple related open reading frames.

Ribonucleases (RNases) degrade mRNA molecules once their translational utility is exhausted, preventing overproduction of proteins.

Unlike other rRNAs transcribed by RNA Polymerase I in the nucleolus, 5S rRNA is transcribed by RNA Polymerase III in the nucleoplasm.

While the 2D layout is a cloverleaf, the functional 3D conformation is an L-shape stabilized by complex non-Watson-Crick hydrogen bonding.