Regulation Of Gene Expression

Question 1

Gene Expression

Answer 1

Turning on the expression of a protein or building of proteins

Question 2

Why is being able to turn off gene expression useful for a cell

Answer 2

So I can stop the production of that protein and save energy

Question 3

Production of a protein

Answer 3

Done after transcription and translation

Question 4

Constitutively expressed genes

Answer 4

Are always expressed
The protein is critical for the function of the cell and if it stops being expressed this so I will probably die

Ex enzymes essential to metabolism

Question 5

Adaptively expressed genes

Answer 5

Genes used in different situations, expressed only one advantage to the cell

Induction: Turning on the transcription of a gene

Repression: turning off the transcription of a gene

Question 6

Constitutively and adaptively expressed genes

Answer 6

Are all controlled at the genetic level by operons.

Ex: lac operon & trp operon

Question 7

Induction gene (inducible)

Answer 7

(Adaptive)

Example: light sensor that turns on when you walk into a room.

Question 8

Repression gene

Answer 8

(Adaptive)

Always on unless market is gone Factory always making something. Always selling, market goes away and turns off factory.

Question 9

Why is the bacterial regulation of gene expression largely at the pre-transcriptional level?

Answer 9

Because There is no physical separation between the messenger RNA and the ribosomes there’s no way to keep them apart so in messenger RNA is produced the ribosomes grab the mRNA and start to turn it into a pro Tien immediately and because it can’t stop the ribosome from doing its job the only way to bacterial cell can regulate is by not making any messenger RNA and control things going on at the transcriptional level.

*only way to control is by stopping the form of mRNA by Turing on or off the expression. (RNA polymerase)

Question 10

The only enzyme that does transcription

Answer 10

Creates RNA
RNA polymerase
(Reads along the template strand of DNA uses the info to form complementary RNA strand, which becomes the messenger RNA that goes to the ribosome )

Question 11

Structure of an operon

Answer 11

Promoter 
RNA polymerase 
Repressor protein 
Operator
Structural gene

Question 12

Operon

Answer 12

Set of genes and the elements that control their expression

Question 13

Promoter

Answer 13

Where RNA polymerase binds/starts process of transcription by recognizing the the template strand.

Question 14

RNA polymerase (rna pol)

Answer 14

Makes mRNA from structural genes

Question 15

Repressor protein

Answer 15

When active, prevents rna polymerase from moving along dna. Sits on operator

Question 16

Operator

Answer 16

Where repressor binds (sequence of DNA)

Question 17

Structural genes (dna)

Answer 17

Encode for proteins whose expression is regulated by the operon
Enzymes used for something

Question 18

What is the lac operon involved in

Answer 18

The expression of enzymes that can break down the sugar lactose

Question 19

Main enzyme in breaking down lactose

Answer 19

Beta galactosidase (gene 6)

Digests lactose( disaccharide ) into glucose and galactose (monosaccharides)

Question 20

The Lac operon

Answer 20

Inducible gene expression
(Adaptive gene)
Turns on B gal enzyme when lactose is present by sticking to the repressor

Letting rna polymerase to produce mRNA

Digesting the lactose

Question 21

If operator and repressor don’t exist

Answer 21

Then nothing can stop rna polymerase from working

Question 22

When looking at an operon your going to see the same overall structure

Answer 22

Promoter, operator and structural genes

Simplified version

Question 23

Terminator

Answer 23

Where RNA polymerase stops

Question 24

The lac repressor protein

Answer 24

Is expressed continuously for operon to function. With its own promoter and repressor protein gene (lack) no operator present, so no way to stop expression.

Question 25

The constant expression of a gene is

Answer 25

Constitutive expression (no operator)

It is the characteristic of these repressor proteins.

Constitutive Promoter, repressor protein, terminator. /adaptive Then another promoter, operator, structural genes, terminator

Question 26

What substance induces the expression of beta galactose

Answer 26

Lactose

Question 27

Suppose there was a mutation in the operator that caused it to no longer bind to the repressor pro Tien will gene expression be on or off?

Answer 27

Constantly on
Becomes constitutive
Will be making beta galactosidase over and over until it works itself to death

Question 28

Suppose there it was a mutation and better galactosidase enzyme that caused it to be catalytically inactive. Well this operon work as intended

Answer 28

When lactose is in the cell: expression is on, makes enzyme but it’s broken and can’t digest lactose. Cell eventually dies.

Question 29

If we change the repressor proteins so that it no longer binds to lactose will we ever be able to express Beta galactosidase

Answer 29

No it will always be stuck to operator, expression will always be off.

Question 30

Repressible protein vs inducible protein

Answer 30

Both adaptive.

Only difference is the behavior of the repressor protein

Question 31

Repressible gene expression operon example

Answer 31

Trp operon
Operon that makes the amino acid tryptophan
Usually in the on position
Negative feedback ( too much trp from outside enzymes are not made)

Question 32

Is the TRPR Gene inducible or constitutively expressed

Answer 32

Constitutive because there is no operator

Trpr is the gene that creates the repressor protein for trp operon

Repressor protein is always expressed because there is no operator

Question 33

Bacterial cells

Bacterial gene regulation

Answer 33

This is what happens in bacterial cells as the only form not really as used to be able to control the expressions of protein mainly because the expression of mRNA and the creation of protein happens essentially at the same time there is no separation between messenger RNA and a protein so the only way bacteria Sask have to stop expression of a protein is to throw up a roadblock in the front of RNA polymerase and the roadblock will stop that expression of that material.