RNA TRANSCIPRTION, GENETIC CODE, & TRANSLATION

Vocabulary flashcards covering essential terms and definitions from the lecture notes on RNA transcription and translation.

mRNA

Messenger RNA; carries protein-coding information from DNA; mainly produced by RNA polymerase II in eukaryotes.

rRNA

Ribosomal RNA; structural and catalytic component of the ribosome.

tRNA

Transfer RNA; adapter that delivers amino acids to the ribosome and contains an anticodon.

RNA polymerase

Enzyme that synthesizes RNA from a DNA template; uses NTPs; no primer; transcription proceeds 5'→3'.

Promoter

DNA sequence that defines where transcription starts and recruits RNA polymerase.

Transcription Start Site (TSS)

Position where RNA synthesis begins, determined by promoter elements.

Pribnow box

Bacterial -10 promoter element with consensus sequence TATAAT; aids RNA polymerase binding.

Sigma factor

Bacterial transcription factor that directs RNA polymerase to specific promoters and then dissociates.

Holoenzyme

RNA polymerase bound to sigma factor; higher affinity for promoter DNA.

Core RNA polymerase

RNA polymerase without sigma factor; binds DNA with similar affinity to promoter or non-promoter.

Termination

Process by which transcription ends at a terminator; can be rho-dependent or independent.

Rho-dependent termination

Termination requiring the rho helicase to dissociate the transcription complex.

RNA Pol II

Main eukaryotic RNA polymerase that transcribes mRNA and some snRNA/miRNA genes.

TATA box

Promoter element in eukaryotes (~-25 to -30) where TBP binds to help recruit transcription machinery.

TBP

TATA-binding protein; part of basal transcription factors guiding RNA polymerase II recruitment.

5' cap

5’-methyl guanosine cap added to the 5' end of pre-mRNA; promotes stability and translation.

5' cap synthesis

Three-step process: remove one phosphate, add GMP, then methylate the guanine.

PolyA tail

Addition of a polyadenine tail at the 3' end of mRNA; enhances stability and export.

AAUAAA

Polyadenylation signal sequence directing poly(A) tail addition.

RNA splicing

Removal of introns and joining of exons to produce mature mRNA.

Spliceosome

Ribonucleoprotein complex containing snRNAs that carries out splicing.

Intron

Noncoding sequence removed during RNA processing.

Exon

Coding sequence retained in mature mRNA.

RNA editing

Post-transcriptional modification that can alter nucleotide sequence, e.g., C to U deamination.

Inosine

Modified nucleoside in tRNA that broadens codon recognition (wobble base pairing).

Alternative splicing

Different exon–intron combinations from one transcript yield multiple mRNA variants.

Genetic Code

Triplet codon language translating mRNA to amino acids; largely universal across organisms.

Open Reading Frame (ORF)

Segment from start codon to stop codon that is translated into protein.

Start codon

AUG; initiates translation; in bacteria often corresponds to formylmethionine (fMet).

Methionine

Initiator amino acid in translation; fMet in bacteria, Met in eukaryotes.

tRNA anticodon

Anticodon loop on tRNA that base-pairs with the mRNA codon during translation.

Wobble base pairing

Flexibility in codon-anticodon pairing, especially at the third codon position.

Aminoacyl-tRNA synthetase

Enzyme that charges tRNA with the correct amino acid; high fidelity with editing.

Aminoacylation (tRNA charging)

Two-step reaction attaching amino acid to tRNA using ATP to form aminoacyl-adenylate, then transfer to tRNA.

Second genetic code

Identity elements in tRNA that ensure the correct amino acid is attached by aaRS.

Translation

Process of synthesizing a polypeptide from mRNA; consists of initiation, elongation, termination.

Ribosome

Ribonucleoprotein complex with rRNA and proteins; two subunits; catalyzes protein synthesis.

Peptidyl transferase

Ribozyme activity of the rRNA (e.g., 28S) that forms peptide bonds between amino acids.

Polysomes

Multiple ribosomes simultaneously translating a single mRNA.

Release factors

Proteins recognizing stop codons and catalyzing hydrolysis to release the polypeptide.

Shine-Dalgarno sequence

Bacterial ribosome-binding site that pairs with 16S rRNA to position the start codon.

fMet

Formylmethionine; initiating amino acid in bacterial protein synthesis.

80S ribosome

Eukaryotic cytoplasmic ribosome (40S + 60S subunits).