16 Gene Expression

3' UTR

Region just downstream of the protein-coding region in an RNA molecule that is not translated.

5' cap

A methylated guanosine triphosphate (GTP) molecule attached to the 5' end of a messenger RNA to protect it from degradation.

5' UTR

Region just upstream of the protein-coding region in an RNA molecule that is not translated.

activator

Protein that binds to prokaryotic operators to increase transcription.

catabolite activator protein (CAP)

Protein that complexes with cAMP to bind to promoter sequences of operons controlling sugar processing when glucose is not available.

cis-acting element

Transcription factor binding sites within the promoter that regulate the transcription of a gene adjacent to it.

Dicer

Enzyme that chops the pre-miRNA into the mature form of the miRNA.

DNA methylation

Epigenetic modification that leads to gene silencing by adding a methyl group to the DNA molecule.

enhancer

Segment of DNA that influences the transcription of a specific gene, located upstream, downstream, or on another chromosome.

epigenetic

Heritable changes that do not involve changes in the DNA sequence.

eukaryotic initiation factor-2 (eIF-2)

Protein that binds first to an mRNA to initiate translation.

gene expression

Processes that control the turning on or off of a gene.

guanine diphosphate (GDP)

Molecule left after energy is used to start translation.

guanosine triphosphate (GTP)

Energy-providing molecule that binds to eIF-2 and is needed for translation.

histone acetylation

Epigenetic modification that leads to gene expression by adding or removing an acetyl functional group.

inducer

Small molecule that activates or represses transcription.

inducible operon

Operon that can be activated or repressed depending on cellular needs and the environment.

initiation complex

Protein complex containing eIF-2 that starts translation.

lac operon

Operon in prokaryotic cells that encodes genes required for processing and intake of lactose.

large 60S ribosomal subunit

Second, larger ribosomal subunit that binds to RNA to translate it into protein.

microRNA (miRNA)

Small RNA molecules (approximately 21 nucleotides) that bind to RNA molecules to degrade them.

myc

Oncogene that causes cancer in many cancer cells.

negative regulator

Protein that prevents transcription.

operator

Region of DNA outside of the promoter that binds activators or repressors controlling gene expression in prokaryotic cells.

operon

Collection of genes involved in a pathway transcribed together as a single mRNA in prokaryotic cells.

poly-A tail

Series of adenine nucleotides attached to the 3' end of an mRNA to protect it from degradation.

positive regulator

Protein that increases transcription.

post-transcriptional

Control of gene expression after the RNA molecule has been created but before it is translated into protein.

post-translational

Control of gene expression after a protein has been created.

proteasome

Organelle that degrades proteins.

repressor

Protein that binds to the operator of prokaryotic genes to prevent transcription.

RISC

Protein complex that binds with miRNA to RNA to degrade it.

RNA stability

How long an RNA molecule will remain intact in the cytoplasm.

RNA-binding protein (RBP)

Protein that binds to the 3' or 5' UTR to increase or decrease RNA stability.

small 40S ribosomal subunit

Ribosomal subunit that binds to RNA to translate it into protein.

trans-acting element

Transcription factor binding site found outside the promoter or on another chromosome that influences transcription of a particular gene.

transcription factor

Protein that binds to DNA at the promoter or enhancer region and influences transcription of a gene.

transcription factor binding site

Sequence of DNA to which a transcription factor binds.

transcriptional start site

Site at which transcription begins.

trp operon

Series of genes necessary to synthesize tryptophan in prokaryotic cells.

tryptophan

Amino acid that can be synthesized by prokaryotic cells when necessary.

untranslated region

Segment of the RNA molecule that is not translated into protein, lying before (5') and after (3') the protein-coding region.