Exam 2 (Ch.16- Gene regulation)

Question 1

Basis of development, cellular differentiation, and physiological cellular responses

Answer 1

differential gene expression

Question 2

1) Transcriptional control (in nucleus)
2) RNA procession control (in nucleus)
3) RNA transport and localization control
4) Translation control
5) mRNA degradation control
6) Protein activity control

Answer 2

What are the six different levels where gene expression can be controlled?

Question 3

since prokaryotic cells have no defined nucleus, transcription and translation both take place in the ___
- both processes occur at the same time

Answer 3

cytoplasm

Question 4

Transcription and translation occur spatially and temporally together in __

Answer 4

prokaryotes

Question 5

gene expression in prokarotes:

structural genes for enzymes that carry out a sequence of related reactions are found together in the

Answer 5

same regulatory region

Question 6

gene expression in prokarotes:

regulatory units are transcribed into a single polycistronic mRNA ____: another term for a gene

Answer 6

cistron

Question 7

gene expression in prokarotes:

ribosomes bind the ____ sequence upstream of the start codon

Answer 7

shine-dalgarno

Question 8

enzymes may be:

Answer 8

• inducible (adaptive) –> lac operon
• constitutive
• repressible –>trp operon

Question 9

What is a model system for studying gene regulation?

Answer 9

The lac operon

Question 10

What two conditions must be met for lac Operon to get activated?

Answer 10

• No glucose available
• lactose present

Question 11

regulatory elements are located ____ of the gene cluster they control and are ___

Answer 11

Upstream; cis-acting

Ex: lac Operator

Question 12

the molecules that bind these cis-acting sites are ____ elements

Answer 12

Trans-acting elements

ex: lac repressor protein

Question 13

negative control of the lac operon:

A ____ binds to the operator and ____ transcription

• occurs when ______ is present

Answer 13

repressor; blocks; no lactose

Question 14

The lac repressor undergoes an ___ change which does allow transcription to proceed

• operator-binding region is altered when bound to ___
• enzyme induction can be a result of relief of ___

(enzyme induction of the lac operon)

Answer 14

allosteric; lactose; repression

Question 15

• no binding occurs; transcription proceeds
• operator binding region of repressor is altered

constitutive

Answer 15

the response of the lac operon in the absence of lactose when a cell bear the I- mutation

Question 16

• nucleotide sequence of operator gene is altered
• no binding occurs; transcription proceeds

constitutive

Answer 16

the response of the lac operon in the absence of lactose when a cell bear the Oc mutation

Question 17

• lactose binding region is altered; no binding to lactose
• repressor always bound to operator, blocking transcription

repressed

Answer 17

the response of the lac operon in the absence of lactose when a cell bear the Is mutation

Question 18

Involved when repressing expression of the lac operon when glucose is present

Answer 18

catabolite-activating protein (CAP)

• the inhibition is called catabolite repression

Question 19

Works by CAP and cAMP binding together and creating an ___ transition which allows RNA polymerase to bind when glucose is absent

• transcription and translation __

Answer 19

allosteric; both occur

Question 20

Catabolite repression of the lac operon: absence of glucose

• cAMP levels ___, resulting in the formation of a ______ which binds CAP to the ____, stimulating ____ (positive control)

Answer 20

increase; CAP-cAMP complex; promoter; transcription

Question 21

Catabolite repression of the lac operon: presence of glucose

• cAMP levels ___, CAP-cAMP complexes are ____
• transcription is _____

Answer 21

decrease; not formed; not stimulated

Question 22

A protein that activated or represses gene transcription

Answer 22

transcription factor

Question 23

• In the ___ of tryptophan, the operon formed by enzymes for tryptophan reproduction is repressed
• tryptophan acts as a ____

Answer 23

presence; co-repressor

(tryptophan production)

Question 24

When tryptophan is present, the tryptophan ____ binds to tryptophan and allosterically transitions and ______

Answer 24

repressor; binds to the operator

Question 25

The tryptophan (trp) Operon in E.coli is a ___

Answer 25

repressible gene system

Question 26

The tryptophan (trp) Operon is activated in the ___ of tryptophan

Answer 26

absence

Question 27

Binds to the operator in the lac operon and binds lactose; it does not bind glucose

Answer 27

The lac repressor

Question 28

gene expression in an operon may be:

Answer 28

• inducible
• constitutive
• repressible

Question 29

turned on when the signal molecule is present
- ex: lac operon

Answer 29

inducible

Question 30

unregulated essentially constant levels of expression

always “on”

Answer 30

Constitutive Genes

Question 31

turned off when the signal molecule is present
- ex: trp operon

Answer 31

repressible

Question 32

the inducer-repressor control of the lac operon is an example of ___ control

Answer 32

negative (expression is normally blocked by the repressor)

Question 33

the CAP-cAMP system of the lac operon is an example of ___ control

Answer 33

positive (expression requires the positive signal of the activator CAP-cAMP bound to the CAP site)

Question 34

the repressor-corepressor control of the trp operon is an example of ___ control

Answer 34

negative (expression is normally blocked by the repressor complex)

Question 35

a genetic unit consisting of one or more structural genes encoding polypeptides, and an adjacent operator gene that regulates the transcriptional activity of the structural gene or genes

Answer 35

operon