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Gene Regulation Flashcards

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1
Q

Gene Regulation

A

Regulating gene expression so that they do it correctly in the right environment

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2
Q

House Keeping genes

A

genes expressed in almost every cell type, they
keep basic cells functions operating normally

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3
Q

Regulated genes

A

Expression of these genes is controlled, they may not be expressed in every cell or at all times in a cell

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4
Q

Levels of Control

A

Transcriptional control

(Pre) translational control

Post translational control

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5
Q

Transcriptional unit

A

the segment of DNA from the start of transcription to the end of transcription

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6
Q

Operon

A

Cluster of Prokaryotic gene organized into a transcriptional unit and its regulatory sequences

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7
Q

Regulatory Sequences

A

DNA binding proteins bind to a DNA sequence within the transcriptional unit to inhibit or enhance gene expression

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8
Q

Promoter

A

site where the RNA polymerase binds to begin synthesis of mRNA

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9
Q

Operator

A

Short Segment to which a regulator (Repressor) binds to affect expression of Operon - controls whether the RNA Polymerase has access to the DNA or not

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10
Q

Regulatory Protein

A

This is a protein that binds to the regulatory sequence and affects the expression of the associated gene

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11
Q

Positive Control:

A

genes expression is enhanced by an activator protein
- gene expression turned on
- gene expression is turned off in the absence or deactivation of the activator

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12
Q

Negative Control

A

Genes expression n is inhibited by a repressor protein
- gene expression turned off
- gene expression is turned on the absence or deactivation of the repressor

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13
Q

What does Lac I code for?

A

Codes for the lac repressor - synthesized in its active form

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13
Q

What is Lac Operon and what is it controlled by?

A

a negative control of transcription for lactose metabolism in prokaryote, this is controlled by the lac repressor which, when lactose is presented, becomes inhibited and thus allows for the production of the Lac enzymes that break down lactose

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14
Q

What does Lac Z code for ?

A

gene that codes for B-Galactosidase - this breaks the bond between galactose and glucose

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15
Q

What does Lac Y code for ?

A

gene that codes for permease which is a protein channel that transports lactose into the cell

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16
Q

What does Lac A code for ?

A

Gene that codes for transacetylase - exports excess sugar from the cell

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17
Q

States of Lac Operon

A

There is an inducer in the operon which is a small molecule that allows for the transcription to occur. That small molecule is allolactose which is converted by B-Galactosidase. When it binds to the lac repressor - it deactivates the repressor.

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18
Q

Lac Operon - Introducing Glucose: when the glucose levels are high..

A

Transcription of the lac operon is inhibited

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19
Q

Lac Operon - Introducing Glucose: when the glucose levels are low..

A

transcription of the lac operon is enhanced when glucose levels are low

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20
Q

CAP Protein

A

Involved in positive regulation and activated by cAMP - binds to the promoter and enables RNA polymerase to bind in order to transcribe

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21
Q

When glucose is low, but lactose is present….

A

lactose converted to allolactose - inactivates repressor
- cAMP at high levels, activated CAP and there is
gene expression

22
Q

When glucose is high, and lactose is present….

A

lactose converted to allolactose which inactivates repressor
glucose inactivates adenylyl cyclase = low/no cAMP, CAP cannot be activated
- no gene expression even though
lactose is present

23
Q

Tryptophan

A

E.Coli need tryptophan…
- when tryptophan is available in the environment, the bacteria do not need to synthesize it. It becomes more energy efficient to stop the growth of tryptophan and it becomes repressed

24
Summary of the Lac operon
Essentially, when there is no lactose, the repressor is always going to be active on the operator, however with there is the presence of lactose, the allolactose which is made by the g-galactosidase, inhibits the repressor and lets the mRNA be transcribed.
25
Long term regulation
regulatory events required for an organism to develop and differentiate
26
Short term regulation
quickly turning off/on genes in response to environmental or physiological needs
27
Trp Operon:
transcriptional unit of 5 genes that code for the biosynthesis of tryptophan Tryptophan works as a corepressor which is a regulatory molecule that activates the repressor to turn off expression of the operon When there is a lot of tryptophan - the molecules bind to the activation site of the repressor - this makes the repressor go and inhibit the transcription of tryptophan
28
Post Transcriptional regulation
determines types and availability of mRNA to ribosomes
29
Transcriptional regulation
determines which genes are transcribed
29
Histone Modifications
When genes are bound to histones, genes cannot be expressed, in order to express gene, it must be accessible
30
Translational regulation
determines rate at which proteins are made
31
Post Translational regulation
determines availability of finished proteins
32
Transcriptional Regulation: Promoters and Enhancers
Promoters: are DNA sequences where RNA polymerase binds to initiate transcription Enhancers: are DNA Sequences that can increase the transcription of specific genes - they are far from the promoter
32
TATA Box
In the promoter site, this is what transcription factors bind to - this is what RNA polymerase binds to
33
Acetylation
Adding acetyl groups to the histones and by doing this you are neutralizing the positive charge from the histone and DNA which loses the bond allowing for transcription
34
Methylation:
Addition of the methyl groups can either activate or repress gene expression
35
Epigenetics
change in gene expression does not involve a change in DNA sequence
36
Genomic Imprinting
methylation that permanently silences the transcription of inherited maternal or paternal allele of a particular gene
37
Repression of Transcription
Repressors - regulatory proteins that inhibit transcription, bind to promoter proximal elements with general transcription factors Corepressor - acts as a bridge between the enhancer and promoter proximal region to repress transcription
37
Promoter Proximal Region
promoter proximal elements (regulatory sequences) ○ Regulatory proteins bind the promoter proximal elements and can either inhibit or enhance transcription
38
Combinatorial gene regulation
different combinations of a small amount of transcription factors can regulate a large array of genes that code for proteins
38
how does the activation of transcription work?
General transcription factors - bind to promoter proximal elements and form RNA Polymerase II Activators - regulatory proteins that enhance transcription ○ Different activators will bind to the enhancer to activate transcription Coactivators - large multi protein complex that forms a bridge between enhancer and promoter proximal region to activate transcription
39
Cell-specific gene regulation
multiple activators are needed for gene transcription, only the cells with those activators will transcribe those genes
40
Coordinated gene regulation
- one signal controls the transcription of all the genes that need to be transcribed together that are controlled by the same regulatory sequence - allows for genes to be transcribed together because eukaryotic cells do not have operons
41
Posttranscriptional Control
Pre-mRNA Processing: - when genes are transcribed, they are not quite mRNA Alternative Splicing: - Exons stay in the mRNA and Introns leave the mRNA - alternative splicing is selecting specific exon combinations to be expressed - meaning that there can be different expressions of the same gene Rate of mRNA breakdown: - the rate at which translation can occur can be controlled RNA Interference (RNAi): - called miRISC which cleaves or inhibits translations: silence mutations
42
Long Noncoding RNAs
- genes that are transcribed to RNA but not translated
43
Process of how miRISC is made
Dicer removes the hairpin, protein complex binds to the miRNA and then cleaves off on of its strands - now it has become miRISC looks for other mRNA that have a complementary sequence and if imperfectly binds can block transcription
44
Post Translational Control
Chemical modification - addition/removal of chemical groups Processing - protein is synthesized as inactive and must be activated to have function - ex) pepsinogen → pepsin Degradation - proteins for degradation get marked with ubiquitin tags and are broken down
45
Genetics of Cancer: Proto-oncogenes
- unmutated genes in normal cells that stimulate cell division
46
Genetics of Cancer: Oncogenes
- mutated proto-oncogenes that causes overactivity in cell division
47
Genetics of Cancer: Tumor suppressor genes
- unmutated genes in normal cells that inhibit cell division - Expressed in balance with proto-oncogenes to produce normal cell growth - Mutations in both alleles of a tumor suppressor gene must be present for it to lose its inhibitory effects on cell division
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Bio 1107 (5 decks)

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