L3: Gene Expression and Operon Regulation Flashcards

Vocabulary practice cards covering gene expression regulation, bacterial operon systems (trp and lac operons), and the components and steps of mRNA translation based on the lecture notes.

Gene Expression

The multi-step process of transcribing a gene into mRNA and subsequently translating that mRNA into a functional protein.

Minus 35 Sequence

A specific sequence located within a gene's promoter region that is recognized by RNA polymerase to start transcription.

Prudenal Box

A promoter sequence located around minus 10 where the replication bubble starts to form.

Operator

A specific DNA sequence in a promoter recognized by regulatory proteins that control when transcription begins.

Repressor

A regulatory protein that binds to a specific operator, physically blocking RNA polymerase from accessing the promoter and preventing transcription.

Inducer

A small molecule that interacts with a repressor to make it detach from an operator, or with an activator to help it bind, thereby initiating transcription.

Co-repressor

A small molecule required by certain repressors to bind an operator and block gene transcription.

Activator

A regulatory protein that binds to a promoter region to assist RNA polymerase in recognizing weak promoters and initiating transcription.

Inhibitor

A small molecule that interacts with an activator protein to prevent it from activating transcription.

Operon

A genetic regulatory structure in bacteria where a single promoter and terminator control the expression of multiple transcribed coding regions.

trp Operon

A bacterial operon containing five transcribed regions under one promoter that code for enzymes required to synthesize the amino acid tryptophan.

trp Repressor

A regulatory protein that blocks transcription of the trp operon only when bound to its co-repressor, tryptophan.

lac Operon

A bacterial operon containing one promoter and three coding regions that produce enzymes allowing the cell to digest lactose for energy.

lac Repressor

A protein that blocks the promoter of the lac operon until bound by its inducer, lactose.

Cyclic AMP (cAMP)

A circular signaling molecule produced by starved bacterial cells breaking down ADP, acting as an inducer for CAP during glucose deprivation.

CAP (Metabolite Activating Protein)

An activator protein that, when bound to cyclic AMP, attaches to the lac operon promoter to turn on transcription in the absence of glucose.

Five Prime Untranslated Region ($5'$ UTR)

The non-coding region at the beginning of an mRNA transcript that precedes the open reading frame and contains ribosome recognition signals.

Three Prime Untranslated Region ($3'$ UTR)

The non-coding sequence at the trailing end of an mRNA transcript following the open reading frame.

Open Reading Frame (ORF)

The central coding sequence of mRNA that a ribosome translates into a chain of amino acids.

Shine-Dalgarno Sequence

A specific sequence located in the $5'$ UTR of prokaryotic mRNA that is recognized by ribosomes to start translation.

Kozak Box

A specific sequence located in the $5'$ UTR of eukaryotic mRNA that is recognized by ribosomes to start translation.

Start Codon

The mRNA sequence $AUG$, which codes for methionine and marks the beginning of the open reading frame.

Transfer RNA (tRNA)

A stem-loop folded RNA molecule with an amino acid attached at its $3'$ end and an anticodon loop that matches mRNA codons during translation.

Anticodon

A three-nucleotide sequence in the bottom loop of a tRNA that base-pairs with a complementary mRNA codon.

Stop Codons

The three mRNA codons ($UAG$, $UAA$, and $UGA$) that signal the end of translation because no complementary tRNAs exist for them.

Release Factor

A protein that recognizes a stop codon in a ribosome's A site, triggering the release of the polypeptide chain, mRNA, and ribosome.

Peptide Bond

The specific covalent bond formed between adjacent amino acids in a growing protein chain.