Test#3 Notes Questions

Question 1

What do structural genes do?

Answer 1

encode proteins

Question 2

What do regulatory genes do?

Answer 2

encode proteins that interact with other sequences and affect the transcription and translation of these sequences

Question 3

What are regulatory elements?

Answer 3

DNA sequences that are not transcribed but play a role in regulating other nucleotide sequences

Question 4

What is the role of gene regulation in bacteria?

Answer 4

maintains internal flexibility, turning genes on and off in response to environmental changes

Question 5

What does gene regulation do in multicellular eukaryotic organisms?

Answer 5

brings about cell differentiation

Question 6

What is constitutive expression?

Answer 6

continuously expressed under normal conditions (some transcription is always happening)

Question 7

What is positive control?

Answer 7

stimulate gene expression

Question 8

What is negative control?

Answer 8

inhibits gene expression

Question 9

What does the structure of an operon consist of?

Answer 9

promotor + additional sequences that control transcription (operator) + structural genes

Question 10

What is a regulator gene?

Answer 10

DNA sequence- encoding products that affect the operon function but are not part of the operon (Lac I)

Question 11

What is an operon?

Answer 11

a single transcriptional unit that includes a series of structural genes, promoter, and operator

Question 12

What are the three genes on the lac operon?

Answer 12

Lac z, lac y, lac a

Question 13

What protein does lac z encode?

Answer 13

b-galactosidase

Question 14

What protein does lac y encode?

Answer 14

permease

Question 15

What protein does lac a encode?

Answer 15

acetylase

Question 16

What stopes the lac operon from being transcribed?

Answer 16

the repressor protein being to the operator sequence which makes it so that RNA polymerase cannot bind to the promotor

Question 17

What encodes for the repressor protein?

Answer 17

the regulatory gene lac I

Question 18

How is the lac operon turned on when lactose is present?

Answer 18

Allolactose binds to the repressor making it inactive because repressor cannot bind to operator

Question 19

What is a negative repressible operon?

Answer 19

The control at the operator site is negative. But such transcription is usually on and need to be turned off. so the transcription is repressible.

Question 20

What is the regulatory protein called in positive transcriptional control?

Answer 20

activator

Question 21

Negative =

Answer 21

repressor

Question 22

positive =

Answer 22

activator

Question 23

inducible =

Answer 23

transcription off

Question 24

repressible =

Answer 24

transcription on

Question 25

What type of operon is the lac operon?

Answer 25

negative inducible

Question 26

What is the inducer for the lac operon?

Answer 26

allolactose

Question 27

What is the lac repressor encoding gene?

Answer 27

lac I

Question 28

What is the lac operon promotor?

Answer 28

lac P

Question 29

What is the lac operon, operon operator?

Answer 29

lac O

Question 30

What is an allosteric binder?

Answer 30

It binds somewhere else other than the active site

Question 31

What does permease do?

Answer 31

makes membrane permeable for lactose

Question 32

What does b-galac do?

Answer 32

breaks it down to either glucose or allolactose

Question 33

Example of an inducer?

Answer 33

allolactose (allows transcription to occur)

Question 34

What happens in the presence of allolactose?

Answer 34

the lac repressor cannot bind to the operator

Question 35

What is a partial diploid?

Answer 35

full bacterial chromosome + an extra piece of DNA on F plasmid

Question 36

Structural gene mutations

Answer 36

affect the structure of the enzymes but not the regulations of their synthesis

Question 37

(-) =

Answer 37

loss of function

Question 38

(+)=

Answer 38

normal

Question 39

What do structural gene mutations do?

Answer 39

affect the structure of the enzymes but not the regulation of their synthesis

Question 40

Effect of regulator-gene mutations?

Answer 40

lacl- leads to constitutive transcription of three structural genes

Question 41

What is catabolite repression?

Answer 41

using glucose when available and repressing the metabolite of other sugars (positive control mechanism)

Question 42

Function of cAMP?

Answer 42

the concentration of cAMP is inversely proportional to the level of available glucose

Question 43

Function of CAP?

Answer 43

The catabolite activator protein (CAP) binds to the promotor of the lac operon and stimulates transcription.

Question 44

Effects of I- mutation?

Answer 44

• total loss of function
• recessive mutation
• still have good copy from other gene, still works/ looks normal

Question 45

What are the results and conclusion of the mutant operator (O^c)

Answer 45

• one lac operon non repressible; mutation is constitutive dominant
• change of sequence of operon
• transcription is never repressed so it is always on

Question 46

What are the results and conclusion of the mutant repressor gene (I^s)

Answer 46

• allolactose can’t bind, no transcription/ uninducible
• cis + trans dominant

Question 47

I d- mutation?

Answer 47

• repressor can’t bind DNA
• always transcription
• dominant negative

Question 48

What type is the tryp operon?

Answer 48

negative repressible
- on when tryp is low
- off when tryp is high

Question 49

What regulates/ changes Eukaryotic chromatin structure?

Answer 49

• Histone modification
• DNA methylation
• Chromatin remodeling

Question 50

Effects of histone modification?

Answer 50

• addition of acetyl groups to histone proteins, acetylation of histones loosens DNA and increases transcription

Question 51

What are the condition for the lac operon to be off?

Answer 51

high glucose, low lactose, low cAMP low LAP

Question 52

What are the condition for the lac operon to be on?

Answer 52

high lactose, low glucose, high cAMP, high CAP