(Lecture 2/3) Transcription, Translation, and Protein Trafficking

Vocabulary flashcards covering transcription, mRNA processing, translation mechanisms, pharmacological inhibitors, and protein trafficking from BIOCD 1520/1521 Module 3.

Gene

A DNA sequence that encodes a functional product, which can be either a protein or a functional RNA molecule.

mRNA (Messenger RNA)

Coding RNA molecules that carry the genetic information required to synthesize proteins, constituting approximately 5% of total cellular RNA.

rRNA (Ribosomal RNA)

Noncoding functional RNA molecules that assemble with ribosomal proteins to form ribosomes, representing approximately 80% of total cellular RNA.

tRNA (Transfer RNA)

Noncoding functional RNA molecules that adapt codons to amino acids during translation, comprising approximately 15% of total cellular RNA.

Xist

A 19 kb long noncoding RNA that coats an X chromosome to silence it for dosage compensation in female mammals.

RNA Polymerase I

The enzyme located in the nucleolus responsible for synthesizing ribosomal RNAs (rRNAs).

RNA Polymerase II

The enzyme located in the nucleus responsible for synthesizing messenger RNAs (mRNAs).

RNA Polymerase III

The enzyme located in the nucleus responsible for synthesizing transfer RNAs (tRNAs) and some rRNAs.

TFIIH

A general transcription factor with helicase activity to unwind DNA and kinase activity to phosphorylate RNA Polymerase II for promoter clearance.

TATA Box

A promoter consensus sequence (TATAWAAR) located -25 to -30 base pairs upstream of the transcription start site that is bound by TBP.

TBP (TATA Binding Protein)

A protein that binds directly to the TATA box consensus sequence to recruit TFIID and the pre-initiation complex.

Enhancer

A regulatory DNA sequence located at a distance from the gene that binds sequence-specific transcription factors to increase transcription levels.

Euchromatin

An open, accessible chromatin structure containing active genes available to RNA Polymerase II and transcription factors.

Heterochromatin

A compact, condensed chromatin structure containing repressed genes that are inaccessible to transcription machinery.

5' Cap

A modified 7-methylguanosine nucleotide added to the 5' end of pre-mRNA that protects against exonuclease degradation and facilitates ribosome binding.

Poly(A) Tail

A stretch of 150 to 250 adenine nucleotides added to the 3' end of mRNA that promotes nuclear export, enhances translation efficiency, and increases stability.

Spliceosome

A nuclear molecular complex consisting of pre-mRNA, 5 small nuclear RNAs (snRNAs), and approximately 50 proteins (snRNPs) that excises introns.

Alternative Splicing

A gene expression process where a single gene pre-mRNA produces distinct protein isoforms by combining different exon arrangements.

Degenerate Genetic Code

The characteristic of the genetic code wherein a single amino acid can be specified by more than one codon.

Aminoacyl-tRNA Synthetase

A high-fidelity enzyme with proofreading activity that attaches a specific amino acid to its corresponding tRNA molecule.

A-site (Aminoacyl-tRNA Site)

The ribosomal site that receives incoming charged aminoacyl-tRNA during translation elongation.

P-site (Peptidyl-tRNA Site)

The ribosomal site that holds the tRNA carrying the growing polypeptide chain.

E-site (Empty/Exit Site)

The ribosomal site where uncharged tRNAs leave the ribosome after peptide bond formation.

Streptomycin

An antibiotic that binds to the bacterial 30S small ribosomal subunit, causing codon misreading and cell death.

Tetracycline

An antibiotic that inhibits bacterial protein synthesis by blocking the binding of aminoacyl-tRNAs to the 30S ribosomal subunit.

Erythromycin

An antibiotic that binds to the bacterial 50S large ribosomal subunit and inhibits ribosome translocation.

Zymogen

An inactive enzyme precursor activated through limited proteolysis, such as the cleavage of trypsinogen into trypsin.

Protein Phosphorylation

The covalent addition of a negatively charged phosphate group to the hydroxyl (-OH) group of Serine, Threonine, or Tyrosine by protein kinases.

Free Ribosomes

Cytosolic ribosomes that synthesize proteins intended for function in the nucleus, mitochondria, peroxisomes, or cytosol.

Bound Ribosomes

Ribosomes attached to the rough endoplasmic reticulum that synthesize proteins destined for lysosomes, the plasma membrane, or secretion.

Signal Sequences

Short amino acid motifs within a protein that act as cellular address labels directing the protein to appropriate organelles.

Signal Recognition Particle (SRP)

A cytosolic complex that binds the N-terminal leader signal of a nascent polypeptide and targets the synthesizing ribosome to the ER membrane translocator.

Preproinsulin

The initial translational product of the insulin gene containing an N-terminal leader signal peptide, Chain B, C-peptide, and Chain A.