BISC 130 - Chapter 16: Regulating Gene Expression

Corresponding Textbook Chapter: https://openstax.org/books/biology-2e/pages/15-2-prokaryotic-transcription

What is the pathway from gene expression to cellular activities?

Gene --> mRNA --> Protein --> Cellular activities.

What does 'expressed' mean in genetics?

Genes that are 'On'; they’re actively being transcribed and translated.

What does 'not expressed' mean in genetics?

'Off', referring to genes that are not being actively transcribed or translated.

In Prokaryotes, in what stage does the control of gene expression via transcription factors take place?

In the transcription stage (DNA → mRNA)

Why don't brain cells use muscle-building instructions?

Brain cells contain instructions to build muscle proteins but don't express them because they only build brain matter.

What is a repressor in transcription regulation?

A type of transcription factor that shuts down transcription levels of genes by preventing/reducing levels of transcription.

What role do activators play in transcription regulation?

Transcription factors that increase gene transcription levels.

What genes make up the lac operon?

lacZ, lacY, and lacA

What happens to the lac operon when lactose is absent?

The lac repressor protein binds to the operator, blocking RNA polymerase from transcribing and repressing expression.

What triggers the lac operon to turn on when lactose is present?

Lactose binds to the lac repressor protein, causing a shape change that prevents it from binding to DNA.

Explain the relationship between glucose and cAMP

If glucose is high, cAMP is low, and vice versa.

Catabolite Activator Protein (CAP) needs what to activiate?

cyclic AMP (cAMP)

If CAP is activated, what can be inferred?

That glucose levels are low. If CAP is actiivated, then cAMP is the reason behind it, and cAMP is only abundant when glucose is low

What is the role of cAMP in the expression of the lac operon?

cAMP binds to CAP, and together they stabilize RNA polymerase to promote strong transcription when glucose levels are low.

What happens to RNA polymerase when glucose is high?

CAP cannot bind DNA without cAMP, leading to low expression of the lac operon.

What are 2 conditions that should be met for lac operons to be strongly expressed?

1. Low levels of glucose

2. Lactose actually being present