Gene Regulation in Prokaryotes and Eukaryotes

What are the characteristics of RNA polymerase in bacterial cells?

RNA polymerase in bacterial cells is made up of multiple protein subunits and can directly bind to the promoter to initiate transcription.

What role does the promoter play in bacterial transcription?

The promoter is a region of DNA upstream of a gene where proteins bind to initiate transcription.

What determines how often a bacterial gene will be transcribed?

The frequency of transcription is determined by how well RNA polymerase binds to the promoter, as they have different affinities.

Why is most transcriptional regulation in bacterial cells considered negative?

Most transcription regulation is negative because it involves repressors that inhibit transcription.

What is an operon and how does it function?

An operon is a cluster of genes transcribed together into a single mRNA molecule, allowing for coordinated production of proteins with related functions.

How do the Lac Repressor and CAP regulate the transcription of the Lac Operon?

The Lac Repressor binds to DNA to prevent transcription when lactose is absent, while CAP binds to cAMP and promotes RNA polymerase binding to enhance transcription.

How does the presence of lactose affect the Lac Repressor?

When lactose is present, it binds to the Lac Repressor, preventing it from binding to DNA and allowing transcription to occur.

What is the effect of cellular energy levels on CAP binding?

High energy (high glucose/ATP) prevents CAP from binding, leading to low transcription, while low energy allows CAP to bind, increasing transcription.

How does the trp repressor control transcription of the trp operon?

The trp repressor binds to the operator when tryptophan is abundant, preventing transcription of the operon.

What is the role of chromatin in eukaryotic gene transcription?

Chromatin inhibits transcription by imposing obstacles that must be loosened for transcription to occur.

What are enhancers and their role in transcription regulation?

Enhancers are binding sites for regulatory transcription factors that can interact with basal transcription factors to facilitate transcription.

What types of RNA does RNA polymerase I, II, and III produce in eukaryotic cells?

RNA polymerase I produces rRNA, RNA polymerase II produces mRNA, and RNA polymerase III produces tRNA and small rRNA molecules.

What processing occurs to mRNA in eukaryotic cells?

Processing includes the addition of a 5' cap, a poly-A tail, and splicing to remove introns and join exons.

How does splicing affect protein diversity?

Splicing can produce multiple final mRNA messages from one gene, leading to different proteins with potentially different functions.

What factors can regulate the amount of protein produced in eukaryotic cells?

Regulation can occur at transcription, mRNA stability, translation rates, and post-translational modifications.

What is the path from gene transcription to protein arrival at the cell membrane in eukaryotic cells?

Transcription occurs in the nucleus, followed by RNA processing, export to the cytoplasm, translation at ribosomes, and transport through the ER and Golgi to the membrane.

What is the basic difference between eukaryotic and prokaryotic cells regarding transcription and translation?

Eukaryotic cells have a nucleus and separate transcription and translation processes, while prokaryotic cells can begin translation before transcription is complete.

How does the presence of tryptophan affect the trp repressor?

High levels of tryptophan lead to its binding to the trp repressor, which then binds to the operator and inhibits transcription.

What is the function of the poly-A tail in mRNA processing?

The poly-A tail increases mRNA stability, is required for export from the nucleus, and affects translation rates.

How do regulatory transcription factors influence gene expression?

Regulatory transcription factors respond to extracellular signals and can enhance or inhibit transcription based on their activity.

What is the significance of the pre-initiation complex in eukaryotic transcription?

The pre-initiation complex forms at the promoter and recruits RNA polymerase to start transcription.

How does the length of the poly-A tail affect translation?

The length of the poly-A tail can increase or decrease the rate of translation of the mRNA.

What happens to mRNA after it is transcribed and processed?

After processing, mRNA exits the nucleus and is translated by ribosomes in the cytoplasm.

What is the role of basal transcription factors in eukaryotic transcription?

Basal transcription factors assist in the recruitment of RNA polymerase to the promoter for transcription initiation.

How do enhancers interact with promoters?

Enhancers can be located far from the promoter and interact through DNA looping to facilitate the binding of transcription factors.

What is the impact of chromatin structure on gene expression?

Tightly packed chromatin can inhibit gene expression by preventing access to transcription machinery.

What is the role of the ribosome in protein synthesis?

The ribosome translates mRNA into a polypeptide chain by facilitating the binding of tRNA and the formation of peptide bonds.