BIOL1201 CH17

Gene expression

Process where DNA directs protein synthesis.

Transcription

Synthesis of RNA using DNA information.

Translation

Synthesis of polypeptides from mRNA.

mRNA

Messenger RNA that carries genetic information.

Ribosomes

Sites where translation occurs.

Template strand

DNA strand used for RNA synthesis.

Coding strand

DNA strand identical to mRNA, except for T/U.

Codons

Three-nucleotide sequences that specify amino acids.

AUG

Start codon for polypeptide synthesis.

RNA polymerase

Enzyme that synthesizes RNA from DNA.

Promoter

DNA sequence where RNA polymerase binds.

Terminator

Sequence signaling the end of transcription.

Transcription unit

Stretch of DNA that is transcribed.

Transcription factors

Proteins that assist RNA polymerase binding.

TATA box

Promoter crucial for initiation in eukaryotes.

RNA processing

Modification of pre-mRNA before cytoplasm export.

5' cap

Modified nucleotide added to 5' end of mRNA.

Poly-A tail

String of adenine nucleotides added to 3' end.

Introns

Noncoding segments removed during RNA processing.

Exons

Coding regions that are expressed in mRNA.

Spliceosomes

Complexes that remove introns from pre-mRNA.

Ribozymes

Catalytic RNA molecules that splice RNA.

Alternative RNA splicing

Process allowing different polypeptides from one gene.

Transfer RNA (tRNA)

Molecule that transports amino acids to ribosomes.

Aminoacyl-tRNA synthetase

Enzyme that matches tRNA to its amino acid.

Wobble

Flexibility in tRNA-codon pairing.

Ribosomal subunits

Large and small components of ribosomes.

P site

Ribosome site holding growing polypeptide chain.

A site

Ribosome site for next amino acid tRNA.

E site

Ribosome exit site for discharged tRNAs.

Release factor

Protein that terminates translation at stop codon.

Polyribosome

Multiple ribosomes translating a single mRNA.

Point mutations

Changes in a single nucleotide pair.

Silent mutations

Mutations with no effect on amino acid.

Missense mutations

Mutations coding for incorrect amino acid.

Nonsense mutations

Mutations creating a stop codon prematurely.

Frameshift mutation

Alteration of reading frame due to insertions/deletions.

Mutagens

Agents causing mutations in genetic material.