Gene Regulation in Molecular Biology

This set of flashcards covers key concepts related to gene regulation mechanisms in both prokaryotes and eukaryotes, focusing on transcription factors, regulatory elements, and the roles of effectors in gene expression.

What are the seven points at which gene expression can be regulated?

1. Transcription initiation 2. Post-transcriptional processing 3. RNA stability 4. Translation 5. Protein modification 6. Protein transport 7. Protein degradation

How do prokaryotes primarily regulate gene expression?

At the transcriptional level, by turning genes on or off.

What are the key differences in gene expression regulation between prokaryotes and eukaryotes?

Prokaryotes regulate primarily at transcription, while eukaryotes regulate at multiple levels including epigenetic and post-translational.

What do transcription factors do?

They recognize and bind to specific DNA sequences to either promote or inhibit transcription.

What is the role of an activator in gene regulation?

An activator increases the rate of transcription initiation by recruiting or stabilizing RNA polymerase.

What is a repressor and how does it function?

A repressor decreases or prevents transcription initiation by blocking RNA polymerase binding or inhibiting activator function.

What are cis-acting elements?

Specific DNA sequences that regulate the expression of a gene located on the same DNA molecule, such as promoters and enhancers.

What is the function of co-activators in gene regulation?

Co-activators enhance transcription by bridging activators and the basal transcription machinery without direct contact with DNA.

What is the Mediator complex?

A multi-protein complex that acts as a master co-activator for Pol II, bridging activators and RNA polymerase.

How do effectors regulate gene expression?

Effectors bind to activators or repressors, causing conformational changes that increase or decrease transcription.

What is the default expression status of bacterial genes?

ON, because their DNA is relatively open and accessible to RNA polymerase.

What is the default expression status of eukaryotic genes?

OFF, due to the chromatin packaging that inhibits access to RNA polymerase.

What is the significance of enhancers in gene expression?

Enhancers are DNA elements that act at a distance to significantly increase the transcription of associated genes.

What is the role of small RNAs in gene regulation?

Small RNAs can bind to mRNAs and regulate gene expression by repressing translation or triggering mRNA decay.

What is the difference between miRNAs and siRNAs?

miRNAs are endogenous and regulate multiple genes through partial complementarity, whereas siRNAs are typically exogenous or perfectly complementary to a single mRNA.

Describe the Helix-Turn-Helix motif in transcription factors.

It is a common motif in bacterial regulators, consisting of two short helices connected by a turn, facilitating DNA binding.

What are the key features of transcription activation domains?

They are modular, short, lack stable structure until binding, involve varied amino acid composition, and focus on interactions with other proteins.