6.3 Flashcards (Q4 Extra Credit)

Regulation of Gene Expression & Cell Specialization

Operon

A functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter, within which multiple genes are transcribed together to produce a single mRNA molecule.

Regulator gene

A segment of DNA that produces a regulator protein to control the expression of one or more other genes.

Repressor

A protein that binds to an operator region of DNA to inhibit transcription of a gene or group of genes.

Corepressor

A small molecule that binds to a repressor protein and enhances its ability to inhibit gene transcription.

Promoter

A DNA sequence that enables the transcription of a particular gene by providing a binding site for RNA polymerase and transcription factors.

Operator

A segment of DNA to which a repressor binds, controlling access to the promoter and thus regulating gene expression.

Structural genes

Genes that encode proteins needed for cell structure and function.

Inducer

A small molecule that initiates the expression of a gene or group of genes by binding to a repressor protein, thereby preventing it from inhibiting transcription.

Epigenetic inheritance

The transmission of information from one generation to the next that affects traits without altering the DNA sequence.

Methylation

the process by which a methyl group (CH₃) is added to DNA, typically at cytosine bases, which can alter gene expression without changing the DNA sequence.

Acetylation

A chemical reaction that introduces an acetyl functional group (CH₃CO) into an organic molecule, replacing an active hydrogen atom.

Transcription factors

Proteins that control gene expression by binding to specific DNA sequences.

Stem Cell

Undifferentiated master cells that can self-renew and differentiate into various specialized cell types, acting as a repair system for the body.

Cell specialization

The process where unspecialized stem cells develop distinct structures and functions to efficiently perform specific roles within a multicellular organism.

Transcription activator/repressor

Regulatory proteins (transcription factors) that manage gene expression by binding to DNA near a gene's promoter.

Enhancer/Silencer

Cis-regulatory DNA sequences that control gene expression.

Posttranscriptional control

Regulates gene expression after transcription but before translation.

sRNA (small RNA)

Short, non-coding RNA molecules (typically 40–500 nucleotides) that serve as crucial regulators of gene expression, particularly in bacteria.

miRNA (micro RNA)

Small (17–27 nucleotides), non-coding RNA molecules that act as master regulators of post-transcriptional gene expression in eukaryotes.

siRNA (small interfering RNA)

A class of double-stranded, non-coding RNA molecules, typically 20-24 base pairs in length, that play a key role in the RNA interference (RNAi) pathway to downregulate gene expression.

RNA interference

A biological process where double-stranded RNA molecules inhibit gene expression or translation by neutralizing targeted mRNA molecules.

Translational control

Governs protein synthesis by regulating mRNA efficiency, allowing rapid, reversible responses to environmental stress, growth signals, and nutrient availability.

Post-translational control

The chemical modification of a protein after it has been synthesized, regulating its function, localization, stability, and interactions.

Protease

An enzyme which breaks down proteins and peptides.

Proteasome

A large, multi-subunit protein complex that acts as a cellular "wood chipper," degrading unneeded, misfolded, or damaged proteins marked by ubiquitin into small peptides.

Cellular differentiation

The process where unspecialized stem cells acquire distinct structures and functions to become specialized cells.

Embryonic stem cell

Pluripotent, self-renewing master cells derived from 3- to 5-day-old human embryos.

Adult stem cell

Undifferentiated, multipotent cells found in specific adult tissues—such as bone marrow, skin, and brain—that function to repair and regenerate damaged tissue.