Gene Expression: From Gene to Protein

These vocabulary flashcards cover the key terms and concepts of gene expression, focusing on the mechanisms of transcription, translation, RNA processing, and genetic mutations as discussed in the lecture notes for Chapters 4 and 5.

Gene Expression

The process by which DNA directs the synthesis of protein.

Central Dogma

The standard flow of genetic information characterized by the sequence $DNA \rightarrow RNA \rightarrow Protein$.

Transcription

The first stage of gene expression involving the synthesis of mRNA from a DNA template.

Translation

The second stage of gene expression where mRNA is used by ribosomes to synthesize a protein (polypeptide).

Template strand

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

Coding strand

The non-template DNA strand which is identical in sequence to the mRNA (except DNA has thymine and RNA has uracil).

TATA box

A specific promoter sequence found in all genes where transcription factors bind to initiate transcription.

Transcription factors (TFs)

Proteins that bind to the TATA box and recruit RNA polymerase II to form the transcription initiation complex.

RNA polymerase II

The enzyme that unwinds the DNA and transcribes the template by adding complementary nucleotides to the $3'$ end of the growing transcript.

Pre-mRNA

The initial transcript resultant from transcription that contains both introns and exons before undergoing RNA editing.

Introns

Internal non-coding sequences within a pre-mRNA molecule that are removed during RNA splicing.

Exons

The coding regions of a pre-mRNA molecule that are joined together to form the final messenger RNA (mRNA).

5' cap

A modified nucleotide added to the $5'$ end of pre-mRNA to help with export, protection from enzymes, and ribosome attachment.

Poly-A tail

A sequence of adenine nucleotides added to the $3'$ end of pre-mRNA to facilitate cytoplasmic export and protect the mRNA.

RNA splicing

The process in the nucleus where introns are removed and exons are joined to create a mature mRNA molecule.

Spliceosomes

Protein-RNA complexes that bind to and excise introns during the editing of pre-mRNA.

Codon

A triplet sequence of nucleotides in mRNA that encodes for a specific amino acid.

Redundancy

A property of the genetic code where more than one codon may encode for the same amino acid, helping prevent deleterious mutations.

Transfer RNA (tRNA)

RNA molecules that transfer specific amino acids to the growing polypeptide chain in a ribosome by recognizing mRNA codons.

Anticodon

The nucleotide triplet on a tRNA that base pairs in an antiparallel fashion with a complementary codon on the mRNA.

P site

The binding site in a ribosome that holds the tRNA carrying the growing polypeptide chain.

A site

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

E site

The exit site of the ribosome where discharged tRNAs leave after their amino acid has been added to the chain.

Start codon

The codon $AUG$, which signals the start of translation and codes for the amino acid methionine.

Stop codons

The mRNA sequences $UAA$, $UAG$, and $UGA$, which signal the termination of translation.

Release factor

A protein that binds to the A site when a stop codon is reached, causing the addition of a water molecule and the release of the polypeptide.

Signal-recognition particle (SRP)

A protein-RNA complex that binds to a signal peptide on a growing polypeptide and targets it to the ER membrane.

Point mutations

Chemical changes in just one nucleotide pair of a gene.

Silent mutations

Nucleotide-pair substitutions that have no effect on the amino acid produced due to the redundancy of the genetic code.

Missense mutations

Substitutions that change one amino acid to another within a protein sequence.

Nonsense mutations

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

Frameshift mutation

A mutation resulting from the insertion or deletion of nucleotides that alters the triplet reading frame of the genetic message.