Gene Regulation

Question 1

Reasons for gene regulation

Answer 1

Give cell specialized role
Gene product dosage (not too much or too little)
Respond to changing environmental stimuli
Different developmental stages

Question 2

Housekeeping genes

Answer 2

Always expressed/transcribed (constitutively expressed)
Gene product is needed to run cell
Examples: rRNA, actin, GAPDH (gene whose product is essential in glycolysis), etc.

Question 3

Conditionally expressed genes

Answer 3

Transcription and expression is more regulated
Transcribed and translated in response to need of cell (facultatively expressed)
Examples: Hox genes, cell cycle dependent genes, neurotransmitters, immune response genes, etc.

Question 4

Chromosome territory

Answer 4

Each chromosome exists in a defined area of the nucleus

Question 5

Interchromosomal domain

Answer 5

Areas of the nucleoplasm between chromosomes (space)

Question 6

Transcription factory

Answer 6

Clusters of transcriptional machinery

Located close to highly expressed genes

Question 7

Core promoter

Answer 7

Sequences of DNA that are bound by general transcription factors, causing recruitment of polymerase and basal transcription
Located immediately upstream from +1 site

Question 8

Regulatory segments of the euk gene

Answer 8

Set of cis-acting (next to) sequence elements bound by trans-acting (from someplace else) factors
Contains core promoter, proximal elements (close to core promoter; enhancers or silencers), and distal elements (far away from core promoter; may be on other chromosome; enhancers or silencers)

Question 9

Enhancers

Answer 9

Sequences of DNA that are bound by proteins called activators
When bound, transcription of gene is increased
Located further downstream or upstream from +1 site

Question 10

Silencers

Answer 10

Sequences of DNA that are bound by proteins called repressors
When bound, transcription of gene is decreased
Located further downstream or upstream from +1 site

Question 11

Activators

Answer 11

Proteins that bind to enhancers, causing increased transcription of genes
2 major domains: DNA binding domain and transcription activation domain
Change shape, allow for binding to DNA

Question 12

Response elements

Answer 12

Regions of DNA
Binding to these allows for the cell to respond to environmental change by expressing genes involved in that response
Ex: ARE (antioxidant response element)

Question 13

Repressors

Answer 13

Proteins that bind to silencers, causing decreased transcription of genes

Question 14

Combinatorial gene regulation

Answer 14

Each gene has a specific set of regulatory elements that are bound by specific regulatory proteins
Different combinations of set of common regulatory activators cause different genes to turn on
Advantage: don’t have to have different activators for each gene, fail safe mechanism (many activators are needed to turn on gene)

Question 15

Measuring expression of genes

Answer 15

Measure amount of product (RNA and proteins)
Reporter system: put promoter of interest upstream from reporter gene- when promoter is activated, reporter gene is transcribed

Question 16

Chromatin remodeling

Answer 16

Histone core is moved so that the gene is accessible: allows transcription of genes blocked by histone

Question 17

Alternative splicing

Answer 17

One gene can encode more than 1 protein because different combinations of exons are spliced together to create different proteins

Question 18

mRNA turnover

Answer 18

mRNA is degraded in a controlled manner
Half life: point in time at which half of RNA is degraded; depends on structure, proteins bound, and poly A tail length (too short, degraded)

Question 19

Differential translation

Answer 19

mRNA can be stored in such a way so that they aren’t translated right away
Development and stress: mRNA is available in time of need (mRNA is waiting for signal)

Question 20

Proteolysis

Answer 20

Protein degradation

Is performed in response to signals