Gene Expression & Molecular Biology Vocabulary

Vocabulary flashcards covering gene expression, transcription, translation, and related molecular biology concepts.

Gene Expression

Process by which DNA directs protein synthesis through transcription and translation.

Transcription

Synthesis of RNA using a DNA template, producing messenger RNA (mRNA).

Translation

Synthesis of a polypeptide from an mRNA template on ribosomes.

One Gene–One Polypeptide Hypothesis

Concept that each gene encodes a single polypeptide chain.

RNA

Nucleic acid that serves as the bridge between DNA and protein synthesis.

mRNA (messenger RNA)

RNA molecule that carries genetic information from DNA to ribosomes.

Codon

Three-nucleotide sequence in mRNA that specifies an amino acid.

Template Strand

DNA strand used as a template during transcription.

Coding Strand (Nontemplate Strand)

DNA strand not transcribed; sequence matches mRNA except T replaces U.

Genetic Code

Nearly universal set of rules translating codons into amino acids; redundant but not ambiguous.

RNA Polymerase

Enzyme that synthesizes RNA by reading the DNA template strand.

Promoter

DNA sequence where RNA polymerase binds to initiate transcription.

Terminator

DNA sequence that signals the end of transcription in bacteria.

Transcription Unit

Stretch of DNA that is transcribed into an RNA molecule.

TATA Box

Conserved eukaryotic promoter sequence rich in thymine and adenine.

Transcription Factors

Proteins that assist RNA polymerase in binding to DNA and initiating transcription.

Transcription Initiation Complex

Assembly of RNA polymerase, transcription factors, and promoter DNA.

Polyadenylation Signal

Sequence in eukaryotic DNA/RNA instructing RNA polymerase to terminate transcription.

RNA Processing

Modifications to pre-mRNA in eukaryotes before it exits the nucleus.

5′ Cap & Poly-A Tail

Structures added to pre-mRNA ends for protection, nuclear export, and ribosome attachment.

Intron

Non-coding sequence removed from pre-mRNA.

Exon

Coding sequence that remains in mRNA and is expressed.

Spliceosome

Large RNA–protein complex that removes introns and joins exons.

Ribozymes

RNA molecules with catalytic activity, such as self-splicing.

Alternative RNA Splicing

Generation of different mRNAs (and polypeptides) from one gene by varying exon combinations.

Domain

Discrete functional region of a protein often encoded by a single exon.

Exon Shuffling

Evolutionary process of mixing exons between genes to create new proteins.

tRNA (transfer RNA)

Adapter RNA that carries specific amino acids to the ribosome; contains an anticodon.

Anticodon

Three-nucleotide sequence in tRNA complementary to an mRNA codon.

Aminoacyl-tRNA Synthetase

Enzyme that covalently attaches the correct amino acid to its tRNA.

Wobble

Flexible base pairing at the third codon position allowing some tRNAs to pair with multiple codons.

Ribosome

Cellular organelle where translation occurs; contains A, P, and E tRNA-binding sites.

P Site

Ribosomal site that holds the tRNA carrying the growing polypeptide chain.

A Site

Ribosomal site that holds the tRNA with the next amino acid to be added.

E Site

Ribosomal exit site from which discharged tRNAs leave the ribosome.

Polyribosome (Polysome)

Cluster of multiple ribosomes simultaneously translating a single mRNA molecule.

Signal Peptide

Short amino-terminal sequence that directs the ribosome-polypeptide complex to the endoplasmic reticulum.

Signal-Recognition Particle (SRP)

Ribonucleoprotein that binds the signal peptide and guides the ribosome to the ER membrane.

Point Mutation

Change in a single nucleotide pair (includes silent, missense, and nonsense mutations).

Frameshift Mutation

Insertion or deletion that shifts the reading frame of a gene.

Mutagen

Physical or chemical agent that induces mutations; many are carcinogens.

CRISPR-Cas9

Gene-editing system using guide RNA and Cas9 nuclease to cut and precisely modify DNA.

Gene (Modern Definition)

Region of DNA that can be expressed to produce a functional polypeptide or RNA molecule.