2024 AP Bio_Gene Regulation Eukaryotic
Complexity of Gene Expression
Eukaryotic gene expression is more complex and regulated at multiple levels compared to prokaryotes.
Eukaryotic Genome Characteristics
Eukaryotic genomes are larger than prokaryotic genomes.
DNA organization allows specific segments to be accessed as needed.
DNA is wound around histone proteins, influencing accessibility.
Histones can move along the DNA, altering its structure based on signals.
Epigenetic Regulation
Histone Methylation
Causes coiling of DNA, making genes inaccessible and inactive.
Histone Acetylation
Opens up DNA, making genes accessible and active.
Epigenetic Changes
Alter nucleosome spacing and gene expression.
Influenced by development, environmental factors, drugs, aging, and diet.
Linked to diseases such as cancer, autoimmune disorders, mental disorders, and diabetes.
Regulation of Protein Synthesis at DNA Level
Gene regulation is influenced by internal and external signals.
Key components include:
Regulatory Genes: Code for regulatory proteins or RNA.
Transcription Factors: Regulatory proteins that interact with DNA.
Regulatory Sequences: DNA stretches that interact with regulatory proteins.
Eukaryotic Promoter Structure
Most promoters contain the TATA Box.
RNA polymerase requires transcription factors to bind to the promoter first.
Larger promoters allow more transcription factors to bind, enhancing control.
Eukaryotes have three RNA polymerases (I, II, III) for different genes.
Transcription Factors & Regulatory Sequences
Activator Proteins: Increase transcription speed by interacting with enhancers.
Repressor Proteins: Slow or block transcription by interacting with silencers or blocking transcription factors.
Activator and Repressor Dynamics
Gene expression depends on the presence of activators and absence of repressors.
Different combinations of activators and repressors lead to varied transcription levels.
Levels of Gene Regulation
Pre-transcriptional Level: Chromatin accessibility and transcription factors.
Post-transcriptional Level: RNA processing and stability.
Post-translational Level: Protein modifications and degradation.
Post-transcription Regulation
Allows rapid adjustment of gene expression in response to environmental changes.
Alternative Splicing: Produces different mRNAs from the same pre-RNA.
RNA Interference (RNAi): Small RNAs can degrade mRNA or block translation.
Variation in Gene Regulation
Within Similar Cells: Cells in a tissue can behave differently.
Between Different Cell Types: Different responses to the same signals.
Between Organisms: Gene regulation accounts for differences in organisms with similar genes.
Coordinating Gene Expression
Genes located far apart can be regulated together if they share transcription factors.
Transcription factors can lead to sequential gene expression.
Cell Differentiation
All cells are genetically identical, but only certain genes are active.
Different gene expression combinations lead to cell specialization.
Signaling and Development
Homeotic Genes: Control body segment formation and organ development.
Hox Genes: A type of homeotic gene that regulates body segmentation.
Hox Genes Structure
Contain a homeobox segment coding for a transcription factor.
Highly conserved across species, indicating a common evolutionary ancestor.
Mutations in Homeotic Genes
Hox genes are expressed in patterns that dictate body segment identity.
Mutations can lead to significant changes in body structure (e.g., fruit fly with two thoraxes).
Hox Genes in Vertebrates
Determine vertebrae types and numbers in animals.
Example: Hoxc-6 in chickens and snakes influences
Complexity of Gene Expression
Eukaryotic gene expression is more complex and regulated at multiple levels compared to prokaryotes.
Eukaryotic Genome Characteristics
Eukaryotic genomes are larger than prokaryotic genomes.
DNA organization allows specific segments to be accessed as needed.
DNA is wound around histone proteins, influencing accessibility.
Histones can move along the DNA, altering its structure based on signals.
Epigenetic Regulation
Histone Methylation
Causes coiling of DNA, making genes inaccessible and inactive.
Histone Acetylation
Opens up DNA, making genes accessible and active.
Epigenetic Changes
Alter nucleosome spacing and gene expression.
Influenced by development, environmental factors, drugs, aging, and diet.
Linked to diseases such as cancer, autoimmune disorders, mental disorders, and diabetes.
Regulation of Protein Synthesis at DNA Level
Gene regulation is influenced by internal and external signals.
Key components include:
Regulatory Genes: Code for regulatory proteins or RNA.
Transcription Factors: Regulatory proteins that interact with DNA.
Regulatory Sequences: DNA stretches that interact with regulatory proteins.
Eukaryotic Promoter Structure
Most promoters contain the TATA Box.
RNA polymerase requires transcription factors to bind to the promoter first.
Larger promoters allow more transcription factors to bind, enhancing control.
Eukaryotes have three RNA polymerases (I, II, III) for different genes.
Transcription Factors & Regulatory Sequences
Activator Proteins: Increase transcription speed by interacting with enhancers.
Repressor Proteins: Slow or block transcription by interacting with silencers or blocking transcription factors.
Activator and Repressor Dynamics
Gene expression depends on the presence of activators and absence of repressors.
Different combinations of activators and repressors lead to varied transcription levels.
Levels of Gene Regulation
Pre-transcriptional Level: Chromatin accessibility and transcription factors.
Post-transcriptional Level: RNA processing and stability.
Post-translational Level: Protein modifications and degradation.
Post-transcription Regulation
Allows rapid adjustment of gene expression in response to environmental changes.
Alternative Splicing: Produces different mRNAs from the same pre-RNA.
RNA Interference (RNAi): Small RNAs can degrade mRNA or block translation.
Variation in Gene Regulation
Within Similar Cells: Cells in a tissue can behave differently.
Between Different Cell Types: Different responses to the same signals.
Between Organisms: Gene regulation accounts for differences in organisms with similar genes.
Coordinating Gene Expression
Genes located far apart can be regulated together if they share transcription factors.
Transcription factors can lead to sequential gene expression.
Cell Differentiation
All cells are genetically identical, but only certain genes are active.
Different gene expression combinations lead to cell specialization.
Signaling and Development
Homeotic Genes: Control body segment formation and organ development.
Hox Genes: A type of homeotic gene that regulates body segmentation.
Hox Genes Structure
Contain a homeobox segment coding for a transcription factor.
Highly conserved across species, indicating a common evolutionary ancestor.
Mutations in Homeotic Genes
Hox genes are expressed in patterns that dictate body segment identity.
Mutations can lead to significant changes in body structure (e.g., fruit fly with two thoraxes).
Hox Genes in Vertebrates
Determine vertebrae types and numbers in animals.
Example: Hoxc-6 in chickens and snakes influences
