BIOL21101 🧬

What is the role of RNA polymerase in prokaryotic transcription?

RNA polymerase transcribes DNA into RNA by binding to promoter regions and synthesizing RNA in the 5' to 3' direction.

Define sigma factors in prokaryotes.

Sigma factors are proteins that bind to RNA polymerase and direct it to specific promoters for transcription.

What is a CRP and its role in transcription?

CRP (cAMP receptor protein) interacts with RNA polymerase to enhance transcription of target genes, often in response to nutrient availability.

What is the significance of co-operative binding in transcription initiation?

Co-operative binding allows multiple RNA polymerase units to bind to the same promoter, increasing the efficiency and stability of transcription initiation.

Describe the importance of riboswitches in gene regulation.

Riboswitches are RNA elements that can change conformation in response to specific metabolites, regulating gene expression by controlling transcription termination or translation initiation.

How do transcription factors function in eukaryotic gene expression?

Transcription factors bind to specific DNA sequences to regulate the transcription of genes by facilitating or inhibiting RNA polymerase binding.

What are the roles of eIF4E and PABP in mRNA translation?

eIF4E binds to the 5' cap of mRNA, while PABP binds to the 3' polyA tail, together enhancing mRNA stability and facilitating translation initiation.

Explain the process of nonsense-mediated decay (NMD).

NMD is a quality control mechanism that degrades mRNAs containing premature stop codons, preventing the synthesis of truncated proteins.

What are the stages of eukaryotic transcription?

The stages include initiation, elongation, and termination, each regulated by specific transcription factors and RNA polymerase.

What is the function of the CTD of RNA polymerase II in eukaryotes?

The C-terminal domain (CTD) coordinates transcription and RNA processing events by interacting with various RNA processing factors.

Describe the concept of catabolite repression in bacteria.

Catabolite repression is a regulatory mechanism that prevents the use of secondary carbon and energy sources when a preferred source, such as glucose, is available.

Identify the difference between leading and lagging strands during DNA replication.

The leading strand is synthesized continuously in the direction of the replication fork, while the lagging strand is synthesized in short segments (Okazaki fragments) in the opposite direction.

What is the role of Dicer in RNA interference (RNAi)?

Dicer is an enzyme that cleaves double-stranded RNA into small interfering RNAs (siRNAs) that guide the RNA-induced silencing complex (RISC) to target and degrade complementary mRNA.

What is the significance of transcription factor gradients during development?

Transcription factor gradients influence cell differentiation by regulating gene expression in a spatially and temporally controlled manner.

Define horizontal gene transfer in bacteria.

Horizontal gene transfer is the movement of genetic material between organisms in a manner other than traditional reproduction, including transformation, conjugation, and transduction.

How do zinc finger transcription factors bind to DNA?

Zinc fingers contain a zinc ion that stabilizes the structure, allowing the protein to fit into the major groove of DNA and interact with specific base sequences.

What are enhancer regions, and how do they affect gene expression?

Enhancers are DNA sequences that promote transcription from a distance and can interact with transcription factors to enhance the expression of associated genes.

Describe the general mechanism of eukaryotic mRNA processing.

Eukaryotic mRNA processing includes capping of the 5' end, splicing out introns, and polyadenylation of the 3' end to form mature mRNA.