Prokaryotic Gene Regulation (Chapter 18.1)
What are the three main structural parts of a prokaryotic operon?
A promoter, an operator, and the structural genes for related enzymes.
At what stages can gene expression be regulated in eukaryotic cells?
At chromatin modification, transcription, RNA processing, translation, and protein processing/degradation.
What happens to genes located in heterochromatin regions?
They are usually inactive because the DNA is tightly packed.
Which scientists proposed early theories of gradual geological change that influenced Darwin?
Hutton and Lyell.
What evidence supports descent with modification from common ancestors?
Homologous structures, fossil records, and molecular similarities.
What happens to the lac operon when lactose is present in the environment?
Allolactose (the inducer) inactivates the repressor, allowing RNA polymerase to transcribe genes for lactose metabolism.
How does histone acetylation affect gene expression?
It loosens chromatin structure, making DNA more accessible for transcription.
What is the function of transcription factors in eukaryotic gene expression?
They help RNA polymerase bind to the promoter and initiate transcription.
What is Darwin’s theory of natural selection?
Individuals with advantageous traits survive and reproduce more, passing those traits on.
What are vestigial structures, and what do they indicate?
Reduced or unused body parts inherited from ancestors.
How does the trp operon regulate tryptophan synthesis in bacteria?
When tryptophan is abundant, it binds to the trp repressor, activating it and turning the operon off.
What are the roles of enhancers and transcription factors in eukaryotic gene expression?
Enhancers are DNA control elements that bind specific transcription factors to increase transcription rates.
What is the role of the TATA box in transcription initiation?
It is a promoter sequence recognized by transcription factors and RNA polymerase II.
How did Darwin’s finches demonstrate adaptive radiation?
Their beak shapes diversified based on available food sources across islands.
What are homologous structures, and how do they differ from analogous structures?
Homologous structures share origin but differ in function; analogous structures serve similar functions but evolved independently.
How does positive control of the lac operon occur when glucose is scarce?
High cAMP levels activate CAP, which binds to the promoter and enhances RNA polymerase binding, increasing transcription.
How do microRNAs (miRNAs) and small interfering RNAs (siRNAs) regulate gene expression?
They bind to complementary mRNA sequences, blocking translation or promoting mRNA degradation.
Describe the typical structure of a eukaryotic gene.
It includes a promoter, exons, introns, and regulatory elements like enhancers.
Which observation by Darwin led to the inference of natural selection?
Populations produce more offspring than can survive, leading to competition.
What is one example of direct observation of natural selection today?
The rise of antibiotic-resistant bacteria or pesticide-resistant insects.
What advantage do operons provide to prokaryotes in changing environments?
They allow coordinated regulation of genes in a single metabolic pathway, conserving energy and resources.
How can mutations in tumor suppressor genes like p53 contribute to cancer development?
Loss of p53 prevents damaged cells from halting the cell cycle or undergoing apoptosis, leading to uncontrolled cell division.
How does chromatin remodeling influence gene expression long-term?
Chemical modifications like methylation can silence or activate genes epigenetically.
How does descent with modification explain both unity and diversity of life?
All species share common ancestry but diverged through adaptation over time.
What embryological evidence supports Darwin’s theory?
Early embryos of vertebrates share similar developmental stages.