Gene expression

Question 1

Why does gene regulation happen?

Answer 1

Not all proteins are required by all cells at all times

Rather, cells regulate gene expression

Question 2

how does gene regulation work/ why is it important?

Answer 2

Housekeeping genes are always needed in a cell and are constantly being transcribed and translated

Transcription factors are proteins that switch genes on by binding to DNA and helping the RNA polymerase to bind

Gene regulation is vital to an organism’s survival and involves turning on or off specific genes depending on the requirements of an organism

Question 3

Gene regulation (in prokaryotes)

Answer 3

Prokaryotes will control gene expression differently than eukaryotes

Prokaryotes are simpler organisms and have one circular strand of chromosomal DNA and circular plasmid DNA

Two examples of gene regulation in prokaryotes:
lac operon
trp operon

Question 4

The lac operon (active form, in-active form)

Answer 4

Gene making enzyme for lactose to be digested

The lac operon consists of a promoter, an operator, and the coding regions

Upstream from the operon is a gene that codes for a repressor protein (lacI)

Active form:
- when lactose isnt present, the lac repressor binds with the operator of the lac operon (after the promoter for RNA polymerase)
- Rna polymerase cannot bind to promoter and transcribe

Inactive form:
- Lactose IS present
- lactose is the inducer, binds with the lac repressor to prevent it from bonding to the lac operator
- turns off when lactose is not present

Question 5

Trp operon

Answer 5

CODING FOR TRYPTOPHAN SYNTHESIZING ENZYMES

The trp operon has an promoter and operator that precedes the genes coding for tryptophan-synthesizing enzymes

Upstream from the operon is a gene that codes for a repressor protein (trpR)

Active form:
- tryptophan is present
- bonds with the trp repressor so it can bond to the operator
- no tryptophan is made

inactive form:
- trp repressor cannot bond to the operator
- tryptophan is made

Question 6

Eukaryotic gene expression (transcriptional, post transcriptional, translational, post-translational)

Answer 6

Transcriptional
- Activator molecules enhance gene transcription by binding upstream of the promoter and initiating changes to histones, either by remodeling proteins or adding acetyl groups to loosen DNA-histone bonds, making DNA accessible.
- Activators or repressors can also influence transcription by affecting transcription factors at the TATA box, altering the transcription rate.

Post transcriptional
- alternative splicing
- masking protiens to prevent from being translated
- altering degradation of mRNA

Translational regulation
- changes to the poly-A tail affects rate of translation

Post-translational regulation
- precessing precursor protiens into active forms (or remain inactive)
- chemical modifications to add or remove chemical groups (to make functional or non-functional)
- degradation of a protien depends on ubiquitin tags