Gene Expression and Protein Synthesis Flashcards

Flashcards for gene expression and protein synthesis

Gene Expression

The process by which DNA directs protein synthesis, including transcription and translation.

Transcription

The synthesis of RNA using information in DNA.

Translation

The synthesis of a polypeptide using information in mRNA.

mRNA

Messenger RNA; carries the genetic code from DNA to ribosomes.

Ribosomes

The sites of translation; where protein synthesis occurs.

Primary Transcript

The initial RNA transcript from any gene prior to processing.

Central Dogma

The concept that cells are governed by a cellular chain of command: DNA -> RNA -> Protein.

Triplet Code

A series of nonoverlapping, three-nucleotide sequences that form the basis of information flow from gene to protein.

Template Strand

The DNA strand that provides the template for ordering the sequence of complementary nucleotides in an RNA transcript.

Codon

An mRNA base triplet that specifies which amino acid will be added to a growing polypeptide chain.

Genetic Code Redundancy

More than one codon may specify a particular amino acid.

Reading Frame

The correct groupings in which codons must be read in order for the specified polypeptide to be produced.

RNA Polymerase

Enzyme that catalyzes RNA synthesis by prying the DNA strands apart and joining together RNA nucleotides.

Promoter

The DNA sequence where RNA polymerase attaches and initiates transcription.

Terminator

In bacteria, the sequence signaling the end of transcription.

Transcription Unit

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

Transcription Factors

Proteins that mediate the binding of RNA polymerase and the initiation of transcription.

TATA Box

A promoter DNA sequence crucial in forming the transcription initiation complex in eukaryotes.

RNA Processing

Modification of pre-mRNA in the eukaryotic nucleus before genetic messages are dispatched to the cytoplasm.

Introns

Noncoding regions of eukaryotic mRNA located between coding regions.

Exons

Coding regions of eukaryotic mRNA that are usually translated into amino acid sequences.

RNA Splicing

The process that removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence.

Alternative RNA Splicing

A process where many genes can give rise to two or more different polypeptides, depending on which segments are used as exons.

Spliceosomes

Complexes of proteins and small RNAs that carry out alternative RNA splicing.

Ribozymes

RNA molecules that function as enzymes.

tRNA

Transfer RNA; transfers amino acids to the growing polypeptide in a ribosome.

Aminoacyl-tRNA Synthetase

Enzyme that facilitates the correct matching between a tRNA and an amino acid.

Wobble

Flexible pairing at the third base of a codon that allows some tRNAs to bind to more than one codon.

rRNA

Ribosomal RNA; found in ribosomal subunits.

A Site

The ribosome binding site that holds the tRNA that carries the growing polypeptide chain.

P Site

The ribosome binding site that holds the tRNA that carries the next amino acid to be added to the chain.

E Site

The ribosome exit site where discharged tRNAs leave the ribosome.

Initiation Factors

Proteins that bring together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits during initiation of translation.

Elongation Factors

Proteins involved in each addition of amino acids during elongation.

Release Factor

Protein that binds to the stop codon in the A site during termination of translation, causing the addition of a water molecule instead of an amino acid.

Signal Peptide

A sequence of amino acids on a polypeptide that marks it for the ER or for secretion.

Signal-Recognition Particle (SRP)

Binds to the signal peptide and brings the signal peptide and its ribosome to the ER.

Polyribosomes (Polysomes)

Strings of ribosomes that can translate an mRNA at the same time.

Mutations

Changes in the genetic material of a cell or virus.

Point Mutations

Chemical changes in just one or a few nucleotide pairs of a gene.

Silent Mutations

Mutations that have no effect on the amino acid produced by a codon because of redundancy in the genetic code.

Missense Mutations

Mutations that still code for an amino acid, but not the correct amino acid.

Nonsense Mutations

Mutations that change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein.

Frameshift Mutation

Alteration of the reading frame of the genetic message, resulting from the insertion or deletion of nucleotides.

Mutagens

Physical or chemical agents that can cause mutations.