linda - regulation of gene expression Flashcards
(30 cards)
Gene Expression in Prokaryotes vs. Eukaryotes
Where does transcription and translation occur in prokaryotes?
Almost simultaneously in the cytoplasm, as there is no nucleus.
Gene Expression in Prokaryotes vs. Eukaryotes
How is gene expression primarily controlled in prokaryotes?
At the level of transcription.
Gene Expression in Prokaryotes vs. Eukaryotes
What separates transcription and translation in eukaryotic cells?
The nuclear membrane.
Gene Expression in Prokaryotes vs. Eukaryotes
At what levels is gene expression regulated in eukaryotes?
Transcriptional, translational, and post-translational levels.
Why Regulate Gene Expression?
Why don’t all genes express all the time in prokaryotes?
To avoid wasting energy; gene expression adapts to the environment.
Why Regulate Gene Expression?
Which genes are typically highly expressed?
Genes for structural proteins.
Why Regulate Gene Expression?
Which genes are usually expressed at low levels?
Regulatory genes.
Transcription Recap
What makes RNA different from DNA?
Ribose sugar, uracil instead of thymine, and it’s single-stranded.
Transcription Recap
What are the three steps of transcription?
Initiation, elongation, termination.
Transcription Recap
What happens during transcription initiation?
RNA polymerase binds and unwinds DNA.
Transcription Recap
What happens during transcription elongation?
RNA polymerase synthesizes mRNA by adding nucleotides.
Transcription Recap
What signals the end of transcription?
RNA polymerase dissociates from DNA (termination).
RNA Polymerase and Promoter Recognition
What direction does RNA synthesis occur?
5’ to 3’ direction.
RNA Polymerase and Promoter Recognition
How does RNA polymerase recognize the promoter?
The sigma subunit binds to -35 and -10 (Pribnow box) sequences.
RNA Polymerase and Promoter Recognition
What are the 5 subunits of bacterial RNA polymerase?
Alpha (2), Beta, Beta prime, Omega, and Sigma.
Termination in Bacteria
What is Rho-independent termination?
Formation of a G-C rich stem-loop followed by uracils causes RNA polymerase to detach.
Termination in Bacteria
What is Rho-dependent termination?
Rho protein binds mRNA and pulls RNA polymerase off DNA.
Mechanisms of Transcriptional Regulation
What are transcription factors?
DNA-binding proteins that enhance or repress RNA polymerase binding.
Mechanisms of Transcriptional Regulation
What are anti-sigma factors?
Proteins that bind sigma factors, preventing RNA polymerase from recognizing promoters.
Operon Regulation - trp Operon
What is an operon?
A cluster of genes under a single promoter, producing polycistronic mRNA.
Operon Regulation - trp Operon
What structural genes are in the trp operon?
trpA to trpE.
Operon Regulation - trp Operon
What regulatory elements are in the trp operon?
Promoter (P), operator (O), leader region with trpL and attenuator.
Operon Regulation - trp Operon
What happens when tryptophan is present?
It binds the repressor, which binds the operator and blocks transcription.
Operon Regulation - trp Operon
What happens when tryptophan is absent?
The repressor is inactive, allowing RNA polymerase to transcribe the operon.
