Ribonucleic acid (RNA)

The size and weight of an mRNA molecule depend entirely on the length of the specific polypeptide chain it is meant to code for.

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

The D-loop gets its name from containing dihydrouracil and plays a key structural role in recognition by aminoacyl-tRNA synthetase.

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

Double-stranded RNA is a hallmark of viral replication; eukaryotic cells use the Dicer and RISC pathways to recognize and destroy it.

Specific identity elements scattered across the acceptor stem and variable loops allow the synthetase to accurately identify its matching tRNA.

The structural domains of rRNA inside the A and P binding sites form precise non-covalent contacts to align the tRNA for peptide synthesis.

The signal recognition particle contains a specific small cytoplasmic RNA molecule known as 7SL RNA, which guides newly synthesizing proteins to the ER.

Double-stranded RNA genomes rely on regular hydrogen bonds between complementary base pairs, specifically adenine-uracil and guanine-cytosine.

RNA polymerases possess the unique biochemical capacity to initiate the synthesis of a new polynucleotide chain completely de novo.

Uncharged tRNAs lack attached amino acids; their buildup indicates that the cell is running low on amino acids to fuel protein translation.

The physical stress of the hairpin combined with the weak hydrogen bonds of the U-rich stretch forces the transcript to detach from the DNA template.

The A (aminoacyl) site welcomes the newly arrived, charged tRNA molecule carrying the next amino acid to be added to the growing peptide chain.

The P (peptidyl) site retains the tRNA molecule attached to the evolving polypeptide chain before transferring it to the incoming A-site tRNA.

Capping enzymes require the 5' triphosphate terminal structure of the nascent RNA transcript to successfully link the inverted guanosine cap.

The anticodon loop exposes three nucleotide bases designed to form anti-parallel hydrogen bonds with the matching mRNA codon triplet.

Eukaryotic structural genes are organized as split sequences where protein-coding regions (exons) are interrupted by non-coding regions (introns).

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

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