BIOL 208 – Exam 4 Lecture Summary: Gene Regulation

Flashcards for BIOL 208 Exam 4 Lecture Summary focusing on Prokaryotic and Eukaryotic Gene Regulation.

Gene Regulation (Prokaryotes)

Enables bacteria to respond to changing environmental conditions by turning specific genes "on" or "off" as needed.

Operon

A stretch of DNA that includes a promoter, operator, and genes of the operon.

Promoter

Binding site for RNA polymerase.

Operator

A regulatory DNA sequence located downstream of the promoter that acts as an "on/off" switch.

Genes of Operon

Cluster of functionally related genes, code for functionally related proteins.

Regulatory Gene

Gene located upstream of the operon that codes for a repressor or activator protein.

Negative Control

Involves repressor proteins that block RNA polymerase (on→off).

Positive Control

Involves activator proteins that enhance RNA polymerase binding (off→on).

Trp Operon

Codes for enzymes that synthesize tryptophan; usually "on" but can be turned "off" when tryptophan is abundant.

Lac Operon

Codes for enzymes that degrade lactose; usually "off" but can be turned "on".

Gene Regulation (Eukaryotes)

Enables cell specialization and allows cells to adapt to internal and external signals by precisely controlling when and where genes are expressed.

Transcriptional Control

Gene expression is regulated by specific DNA sequences.

Promoter (Eukaryotes)

Located near the transcription start site of a gene; binds general transcription factors and RNA polymerase II.

Proximal Control Elements

Located near the promoter region; bind specific transcription factors.

Enhancers

Increase transcription via activator proteins.

Silencers

Decrease transcription via repressor proteins.

Epigenetic Modification

Heritable regulation of gene expression without changes to the DNA sequence.

Euchromatin

Loosely packed chromatin that is transcriptionally active.

Heterochromatin

Densely packed chromatin that is transcriptionally inactive.

Histone Acetylation

Acetyl groups added to histone tails → chromatin opens → increases transcription.

Histone Deacetylation

Acetyl groups removed → chromatin condenses → decreases transcription.

DNA Methylation

Methyl groups (--CH₃) added to cytosines in DNA → reduces transcription.

Epigenetic Inheritance (Cell Division)

Chromatin modifications are heritable across cell divisions; helps cells maintain identity and specialized function in tissues.

Epigenetic Reprogramming

Epigenetic marks are erased and reset during gamete formation and early embryonic development.