Campbell Biology 10e – Chapter 17: Gene Expression

Vocabulary flashcards covering key terms from Chapter 17 (Gene Expression) of Campbell Biology 10th Edition, including major concepts of transcription, RNA processing, translation, and mutation.

Gene Expression

The process by which information encoded in DNA directs the synthesis of proteins (or, in some cases, RNAs); includes transcription and translation.

Transcription

DNA-directed synthesis of RNA, producing an RNA strand complementary to the DNA template.

Translation

RNA-directed synthesis of a polypeptide on a ribosome, using the genetic information encoded in mRNA.

Messenger RNA (mRNA)

RNA molecule that carries a genetic message from DNA to the protein-synthesizing machinery of the cell.

Transfer RNA (tRNA)

Adapter RNA that carries a specific amino acid on one end and has an anticodon that base-pairs with an mRNA codon on the other end.

Ribosomal RNA (rRNA)

RNA component of ribosomes that, together with proteins, forms the catalytic and structural framework of the ribosome.

RNA Polymerase

Enzyme that separates DNA strands and links RNA nucleotides during transcription without requiring a primer.

Promoter

DNA sequence where RNA polymerase binds and initiates transcription.

Terminator

In bacteria, a DNA sequence that signals the end of transcription.

Transcription Unit

The stretch of DNA that is transcribed into an RNA molecule.

Template Strand

The DNA strand that is transcribed; provides the template for ordering RNA nucleotides.

Codon

Three-nucleotide sequence on mRNA that specifies a particular amino acid or a stop signal during translation.

Triplet Code

Genetic code in which sets of three nucleotides (codons) specify amino acids.

Reading Frame

The grouping of mRNA nucleotides into correct, non-overlapping codons for translation.

Start Codon (AUG)

First codon recognized during translation; codes for methionine and sets the reading frame.

Stop Codon

One of three codons (UAA, UAG, UGA) that signal termination of translation.

Genetic Code

Universal set of rules defining how codons specify amino acids; redundant but not ambiguous.

One Gene–One Polypeptide Hypothesis

Modern restatement of Beadle & Tatum’s idea that each gene encodes one polypeptide chain.

Primary Transcript

Initial, unprocessed RNA produced by transcription (pre-mRNA in eukaryotes).

Central Dogma

Concept that genetic information flows from DNA → RNA → protein.

5′ Cap

Modified guanine nucleotide added to the 5′ end of eukaryotic pre-mRNA; aids export, stability, and ribosome binding.

Poly-A Tail

50–250 adenine nucleotides added to the 3′ end of eukaryotic pre-mRNA; enhances stability and translation.

Introns

Noncoding segments of nucleic acid that are removed from pre-mRNA during splicing.

Exons

Expressed sequences that remain in mRNA after splicing and are usually translated.

RNA Splicing

Process that removes introns and joins exons to produce a continuous coding sequence.

Spliceosome

Large RNA-protein complex (snRNPs + proteins) that catalyzes removal of introns from pre-mRNA.

snRNP (small nuclear ribonucleoprotein)

Complex of snRNA and protein that recognizes splice sites and participates in spliceosome assembly.

Ribozyme

Catalytic RNA molecule capable of acting as an enzyme, e.g., some snRNAs in splicing.

Alternative RNA Splicing

Process by which different combinations of exons are joined, producing multiple mRNAs (and proteins) from one gene.

Protein Domain

Discrete, functionally distinct region of a polypeptide; often encoded by separate exons.

Exon Shuffling

Evolutionary process where recombination mixes and matches exons, potentially creating new proteins.

Aminoacyl-tRNA Synthetase

Enzyme that covalently attaches a specific amino acid to its corresponding tRNA.

Wobble

Flexible base pairing between the 3rd base of an mRNA codon and tRNA anticodon, allowing some tRNAs to recognize multiple codons.

Ribosome

Cellular structure composed of rRNA and proteins that coordinates coupling of tRNA anticodons with mRNA codons during protein synthesis.

A Site

Aminoacyl-tRNA binding site on the ribosome that holds the tRNA carrying the next amino acid.

P Site

Peptidyl-tRNA binding site on the ribosome that holds the tRNA with the growing polypeptide chain.

E Site

Exit site on the ribosome where discharged tRNAs leave.

Initiation Factors

Proteins that assemble mRNA, initiator tRNA, and ribosomal subunits at the start codon.

Elongation Factors

Proteins that assist the addition of amino acids during translational elongation.

Release Factor

Protein that binds to stop codon in the A site, triggering release of the polypeptide and disassembly of the translation complex.

Polyribosome (Polysome)

Group of multiple ribosomes translating a single mRNA simultaneously, enabling rapid protein synthesis.

Signal Peptide

Short peptide that directs a growing polypeptide to the endoplasmic reticulum or other locations.

Signal-Recognition Particle (SRP)

Ribonucleoprotein that recognizes the signal peptide and guides the ribosome-polypeptide complex to the ER membrane.

Post-Translational Modification

Chemical changes to a polypeptide (e.g., cleavage, phosphorylation) after translation that make it fully functional.

Point Mutation

Change in a single nucleotide pair of a gene.

Silent Mutation

Nucleotide substitution that does not change the amino acid sequence due to code redundancy.

Missense Mutation

Substitution that changes one amino acid to another in a protein.

Nonsense Mutation

Substitution that converts an amino acid codon into a stop codon, leading to a truncated protein.

Insertion

Addition of one or more nucleotide pairs into a gene sequence.

Deletion

Loss of one or more nucleotide pairs from a gene sequence.

Frameshift Mutation

Insertion or deletion that alters the reading frame, usually leading to nonfunctional proteins.

Mutagen

Physical or chemical agent that interacts with DNA and increases mutation rate.

Polyadenylation Signal

AAUAAA sequence in eukaryotic pre-mRNA that signals cleavage and addition of the poly-A tail.

TATA Box

Promoter DNA sequence (TATAAA) crucial for forming the eukaryotic transcription initiation complex.

Transcription Initiation Complex

Assembly of transcription factors and RNA polymerase II bound to a promoter, ready to initiate transcription.

Metabolic Pathway

Series of enzyme-catalyzed reactions converting substrates into products; mutations in pathway enzymes led to the one gene–one enzyme concept.

Beadle and Tatum

Scientists who established the one gene–one enzyme hypothesis using Neurospora crassa nutritional mutants.

Polymerase II

Eukaryotic RNA polymerase responsible for transcribing mRNA-coding genes.

Domain (Protein)

Modular, independently folding functional region within a protein, often encoded by distinct exons.