Chapter 17: From Gene to Protein

Comprehensive vocabulary flashcards covering Chapter 17: From Gene to Protein, including transcription, RNA processing, translation mechanics, ribosomal anatomy, genetic code properties, and point mutations.

Messenger RNA (mRNA)

A class of RNA that carries genetic information copied from the DNA template to ribosomes, where it directs the synthesis of proteins.

Ribosomal RNA (rRNA)

The structural and catalytic RNA component that, together with proteins, forms the two subunits of a ribosome where protein synthesis takes place.

Transfer RNA (tRNA)

A single-stranded RNA molecule that transports specific amino acids to the ribosome; it contains an amino acid attachment site at one end and an anticodon at the other.

Transcription

The first major stage of gene expression, wherein an RNA transcript is synthesized from a complementary DNA template strand by RNA polymerase.

Translation

The process by which the genetic code carried by an mRNA molecule is decoded by a ribosome to assemble a polypeptide from amino acids.

Promoter

A specific DNA nucleotide sequence where RNA polymerase binds and begins transcription.

TATA Box

A conserved promoter DNA sequence in eukaryotes that helps position transcription factors and RNA polymerase II at the transcription start point.

Transcription Factors

Proteins in eukaryotes that mediate the binding of RNA polymerase II to the promoter and initiate transcription.

Transcription Initiation Complex

The complete assembly consisting of transcription factors and RNA polymerase II bound to a eukaryotic promoter.

$5'$ Cap

A modified guanine nucleotide added to the $5'$ end of a pre-mRNA transcript during eukaryotic RNA processing.

Poly-A Tail

A chain of adenine nucleotides added to the $3'$ end of a pre-mRNA transcript during eukaryotic RNA processing.

RNA Splicing

The removal of noncoding introns and the joining together of coding exons by spliceosomes to generate a mature mRNA molecule with a continuous coding sequence.

Introns

Noncoding segments of nucleic acid intervening between exons in a eukaryotic pre-mRNA transcript that are excised during RNA splicing.

Exons

Coding segments of eukaryotic pre-mRNA transcripts that remain after RNA splicing and are expressed by being translated into amino acids.

Spliceosome

A large cellular complex made up of proteins and small RNAs that cuts out introns from pre-mRNA and splices the exons together.

Protein Domain

A modular structural and functional region of a polypeptide, often coded for by a specific exon.

Codon

A three-nucleotide sequence in mRNA that codes for a specific amino acid or acts as a termination signal during protein translation.

Triplet Code

The genetic arrangement in which three consecutive mRNA nucleotides constitute a single codon specifying one amino acid.

Start Codon

The mRNA codon (AUG) that establishes the reading frame, directs the initiation of translation, and codes for methionine.

Stop Codon

Any of three mRNA codons (UAA, UAG, or UGA) that signal the termination of translation rather than coding for an amino acid.

Anticodon

A nucleotide triplet on one loop of a tRNA molecule that base-pairs complementarily with a corresponding mRNA codon.

Aminoacyl-tRNA Synthetase

The enzyme responsible for attaching the correct amino acid to its corresponding tRNA molecule during amino acid activation.

A Site (Aminoacyl-tRNA Binding Site)

The ribosomal site that binds an incoming aminoacyl-tRNA bearing the next amino acid to be added to the nascent polypeptide chain.

P Site (Peptidyl-tRNA Binding Site)

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

E Site (Exit Site)

The ribosomal site through which deacylated, empty tRNAs leave the ribosome after peptide bond formation.

Release Factor

A protein shaped like tRNA that recognizes a stop codon in the ribosomal A site and promotes the hydrolysis of the bond between the polypeptide and the P-site tRNA.

Polyribosome (Polysome)

A complex formed when several ribosomes translate the same mRNA molecule simultaneously, rapidly making multiple copies of a protein.

Point Mutation

A small-scale genetic change involving the substitution, insertion, or deletion of a single nucleotide base pair in a gene.

Silent Mutation

A nucleotide-pair substitution that alters a codon but does not change the amino acid inserted due to the redundancy of the genetic code.

Missense Mutation

A nucleotide-pair substitution that changes one codon into a codon for a different amino acid, such as the CTC to CAC mutation in sickle-cell $\beta$-globin.

Nonsense Mutation

A nucleotide-pair substitution that changes an amino acid codon into a premature stop codon, causing early termination of translation.

Frameshift Mutation

A mutation caused by the insertion or deletion of nucleotides not in multiples of three, which shifts the reading frame and changes all downstream amino acids.