Gene Regulation

Question 1

How goes transcription occur in bacteria?

Answer 1

RNA polymerase binds to the promoter region

Question 2

Constitutive Genes

Answer 2

Genes that are always expressed in the cell. Housekeeping genes.

Question 3

Where does the majority of regulation in bacteria take place?

Answer 3

Transcriptional level

Question 4

The operator

Answer 4

Area upstream of the promoter. Binding site for proteins that help to regulate gene expression.

Question 5

Repressors

Answer 5

Bind to operator to prevent RNA polymerase from initiating transcription

Question 6

Activators

Answer 6

Bind to an operator and allow RNA polymerase to initiate transcription

Question 7

LacZ

Answer 7

Beta-galactosidase. Protein that is produced when lactose is present. Hydrolyzes lactose to glucose and galactose

Question 8

LacY

Answer 8

Permease. Allows for active transports of lactose across cell membrane.

Question 9

LacA

Answer 9

Transacetylase. Acetylase lactose.

Question 10

LacZ, LacY, LacA

Answer 10

Genes that code for products that are involved in the catabolism of lactose.

Question 11

What is the role of lac?

Answer 11

To break down lactose

Question 12

LacI

Answer 12

Encodes a protein that shuts the system down when lactose is not present

Question 13

What is the inducer for the lac operon?

Answer 13

Allolactose (isomer of lactose)

Question 14

LacZ-, LacY-, LacA-

Answer 14

Structural gene mutations that lead to non-functional proteins

Question 15

LacP-

Answer 15

Non-functional promoter, RNA polymerase can’t bind

Question 16

LacOc

Answer 16

Nonfunctional operator, repressor can’t bind. Constitutive mutation.

Question 17

LacI-

Answer 17

Non functional repressor, unable to bind the operator and turn off transcription

Question 18

LacIs

Answer 18

Super repressor, unable to dissociate from operator. System is always off.

Question 19

Negative control

Answer 19

When a repressor is used to turn the system off (Lac repressor)

Question 20

Positive Control

Answer 20

When an activator protein is used to increase the efficiency of transcription

Question 21

What is e.colis favorite carbon source?

Answer 21

Glucose, it is more efficient. lac is not on in presence of glucose

Question 22

The hunger signal

Answer 22

Binding of CAP/CRP to the promoter, allowing transcription to occurs . CAP or CRP is first activated by cAMP. Lac operon is not expressed without the hunger signal. Must have lactose and the hunger signal for it to be expressed.

Question 23

Cis regulatory elements

Answer 23

DNA binding sites. On the actual DNA. Can bind transcription factor or enhancers.

Question 24

Trans regulatory elements

Answer 24

Modify expression of genes that are distract from the gene that created them. Typically transcription factors or enhancer binding proteins. Bind to Cis. Analogues to LacI

Question 25

Consensus Sequence

Answer 25

Sequence among many genes that isn't exact, but it is similar

Question 26

Basal promoter sequence

Answer 26

Cis regulatory element. Bind transcription factor proteins which are associated with RNA polymerase. Include that CAAT and TATA box.

Question 27

Proximal control regions

Answer 27

These bind transcription factor proteins and are near the promoter

Question 28

Enhancer sequence

Answer 28

Are found far away from the promoter

Question 29

What does the basal transcription machinery do?

Answer 29

Allows a low level of expression

Question 30

What do proximal promoters do?

Answer 30

Increase expression and provide specificity

Question 31

What do enhancer binding transcription factors do?

Answer 31

Provide more specificity and amplify expression further

Question 32

Bending of DNA

Answer 32

Allows an enhancer binding protein to interact with the transcription factor and enhance transcription by RNA polymerase II

Question 33

DNA Binding Domain

Answer 33

Area on trans element transcription factor that only binds specific DNA

Question 34

Dimerization Domain

Answer 34

Two transcription factors that have been bound together to form a functional DNA binding unit.

Question 35

Activator/repressor Domain

Answer 35

Binds to the enhancer binding protein and modulates their function

Question 36

What are the three transcription factors that must dimerize to function?

Answer 36

Zinc finger, helix-turn-helix, and leucine zipper

Question 37

What are the three modes by which transcription factors can act as repressors?

Answer 37

Competition, quenching, and blocking

Question 38

Competition

Answer 38

Binding of the repressor to the enhancer sequence competes for the DNA binding site of the activator

Question 39

Quenching

Answer 39

Repressor protein binds to and interferes with the DNA binding domain of an activator protein. Now the activator cannot bind the enhancer sequence.

Question 40

Blocking

Answer 40

Repressor binds to the activation domain of activator protein and prevent it from interacting with the basal transcription machinery. May reduce transcription levels

Question 41

Response elements

Answer 41

Short sequences of DNA within a gene promoter region that are able to bind a specific transcription factor and regulate transcription of gene. Turn on/off genes

Question 42

Hypoxia Response Elelements

Answer 42

HIf1-a and HIF1-b dimerize and bind to DNA sequences to regulate expression of genes. HIF1a is degraded in the cytosolic under normoxia. Binds to DNA in the nucleus.

Question 43

Mac/myc

Answer 43

Regulatory system for switching between gene activation or repression.

Question 44

In the absence of Myc...

Answer 44

Max form a homodimer and it represses gene transcription

Question 45

In the presence of Myc...

Answer 45

A Myc/Max heterodimer if formed to activate gene expression

Question 46

Myc Overexpression

Answer 46

Distrusts the equilibrium between activation and repression of genes and can lead to cancer. Impairs differentiation and promotes cell proliferation.

Question 47

Burkitt Lymphoma

Answer 47

Caused if Myc is controlling the immunoglobulin promoter and enhancer control system.

Question 48

Drosha

Answer 48

Processes long primary miRNA to pre-miRNA hairpin structures

Question 49

Dicer

Answer 49

Further processes the pre-miRNA to ssRNA and initiates the formation of the RNA induced silencing complex (RISC)

Question 50

What is the main function of miRNA?

Answer 50

To silence genes by preventing translational machinery

Question 51

What are the two modes by which miRNA regulates translation?

Answer 51

Inhibition of translation on the ribosome or degradation of the target mRNA

Question 52

siRNA

Answer 52

Short interfering RNA. Regulates expression at the mRNA level. Processed by dicer.

Question 53

What is the main function of the activated GR?

Answer 53

Up-regulates the expression of anti-inflammatory genes in the nucleus and repressed the expression of pro-inflammatory proteins in the cytosol.