Chapter 17

Gene

A DNA sequence that codes for a functional product

Garrod

Linked genes to enzymes via “inborn errors of metabolism”

Beadle and Tatum

Demonstrated “one gene–one enzyme” hypothesis

Transcription

Synthesis of RNA from DNA template

Translation

Synthesis of polypeptides using mRNA as template

Codon

A three-nucleotide sequence in mRNA that specifies an amino acid

Start Codon

AUG, signals the start of translation

Stop Codons

UAA, UAG, UGA, signal termination of translation

RNA Polymerase

Enzyme that synthesizes RNA

Promoter Region

DNA sequence where RNA polymerase binds to initiate transcription

Transcription Initiation Complex

Assembly of proteins and RNA polymerase at the promoter

5’ Cap

Modified guanine nucleotide added to mRNA for stability and ribosome recognition

Poly-A Tail

String of adenine nucleotides added to mRNA for stability

RNA Splicing

Removal of introns and joining of exons

Spliceosome

Protein-RNA complex that carries out RNA splicing

snRNPs

Small nuclear ribonucleoproteins that help form the spliceosome

tRNA

Transfers specific amino acids to ribosomes during translation

Anticodon

Three-nucleotide sequence on tRNA complementary to mRNA codon

Wobble Effect

Flexibility in base-pairing at the third codon position

Aminoacyl-tRNA Synthetase

Enzyme that attaches amino acids to corresponding tRNA

Polyribosome

Multiple ribosomes translating the same mRNA simultaneously

Release Factor

Protein that recognizes stop codons and terminates translation

Mutations

Changes in DNA sequence

Missense Mutation

Substitution causing a different amino acid

Nonsense Mutation

Substitution creating a premature stop codon

Insertions/Deletions

Addition or loss of nucleotides, potentially causing frameshifts