03/11/2025 Prokaryotic Regulation

Question 1

what is a constitutive gene

Answer 1

it is a gene that is always on and is not regulated

Question 2

what is a repressor

Answer 2

it is a regulatory protein that binds to DNA at regulatory elements and inhibits transcription

Question 3

what is an activator

Answer 3

it is a regulatory protein that binds to DNA and enhances transcription

Question 4

what is negative control

Answer 4

negative control is the transcriptional regulation by repressor proteins

Question 5

what is positive control

Answer 5

it is the transcriptional regulation by activator proteins

Question 6

what controls the repressor and activator proteins?

Answer 6

effector molecules

Question 7

what is the role of an effector molecule

Answer 7

it binds to regulatory proteins and not to DNA
it increases or inhibits transcription

Question 8

what do effector molecules NOT bind to

Answer 8

they do not bind to the DNA

Question 9

if there is no inducer acting on an activator, what is the effect

Answer 9

the activator is not activated and cannot bind to the DNA

Question 10

what is an inducer

Answer 10

it is a type of an effector molecule that increases transcription

Question 11

how do inducers interact with activators?

Answer 11

they bind to them allosterically and allows the activator to bind to the DNA, this allows transcription

Question 12

how do inducers interact with repressors

Answer 12

they bind to them allosterically and do not allow the repressor to bind to the DNA, this allows transcription

Question 13

what type of interaction does the effector have with the regulatory protein?

Answer 13

allosteric, non-covalent interaction that changes the conformation of the protein and either allows/ does not allow the element to bind

Question 14

what are the two types of transcription inhibitors

Answer 14

corepressors and inhibitors

Question 15

what does a corepressor do

Answer 15

it binds to a repressor and allows it to bind to DNA

Question 16

what does an inhibitor do

Answer 16

it binds to an activator and does not allow it to bind to DNA (no activation)

Question 17

if a repressor is bound at the operator, what must occur to start transcription

Answer 17

an inducer must bind to release the repressor

Question 18

if a activator is not bound to DNA and is not activated, what must occur to start transcription

Answer 18

an inducer must bind to allow it to bind to DNA

Question 19

if a repressor is not bound to DNA and we want to stop transcription, what must occur

Answer 19

a corepressor must bind to the repressor to allow it to bind to DNA and stop transcription

Question 20

if a activator is bound to DNA and we want to stop transcription, what must occur

Answer 20

an inhibitor must bind to the activator and cause it to release from the DNA to stop transcription

Question 21

if both the repressor and activator are bound at the same time, will transcription occur

Answer 21

no, the repressor must be off and activator on

Question 22

what is an operon

Answer 22

it is a group of genes that are controlled by one promoter

Question 23

how many mRNA transcripts are produced from an operon

Answer 23

1 transcript

Question 24

if there are multiple genes behind a promoter, will the RNA polymerase produce multiple transcripts

Answer 24

no, it will put all of the coding sequences for the genes into one transcript since it only recognizes the promoter and terminator, not the start and stop codons

Question 25

if you have 3 genes behind an operon, how many start/stop codons are there

Answer 25

3 start codons and 3 stop codons, the number of start codons is equal to the number of genes

Question 26

how is an operon translated?

Answer 26

through a polyribosome where multiple ribosomes are synthesizing different proteins at once

Question 27

why do bacteria form operons?

Answer 27

it allows them to coordinately regulate a group of genes that relate to a common function

Question 28

what are the regulatory elements involved in the lac operon

Answer 28

promoter, CAP binding site, operator

Question 29

what is the role of the promoter

Answer 29

it is where the RNA polymerase binds

Question 30

what is the role of the operator

Answer 30

it is where the lac repressor protein will bind to inhibit transcription

Question 31

what is the role of the CAP site

Answer 31

it is where the CAP binding protein will bind in the absence of glucose

Question 32

what are the structural genes involved in the lac operon

Answer 32

Lac Z, Lac Y, and Lac A

Question 33

what is the role of Lac Z

Answer 33

it encodes the beta galactosidase enzyme which digests lactose and creates allolactose

Question 34

what is the role of Lac Y

Answer 34

it encodes lactose ermease which is a membrane protein that allows the transport of lactose into the cell

Question 35

what is the role of allolactose

Answer 35

it acts as the inducer/ effector molecule that binds to the repressor protein (LacI) and causes it to come off of the operator

Question 36

when the Lac Operon is regulated by a repressor protein, which protein is it? what inducer is involved

Answer 36

the repressor protein is the lac repressor coded by Lac I the inducer is the allolactose that is made in the presence of lactose by Lac Z

Question 37

where is Lac I made?

Answer 37

the repressor protein can be made from anywhere in the cell, this includes plasmids and even manual injection

Question 38

without the genes of Lac Y, can lactose be metabolized?

Answer 38

no, the lactose couldn't even enter the cells as these code for the membrane proteins

Question 39

without the genes of Lac Z, can lactose be metabolized

Answer 39

no, without lactose Z the lactose cannot be metabolized or converted to allolactose

Question 40

what about Lac A? what if we didn't have it?

Answer 40

the lac operon would still be able to metabolize lactose

Question 41

what is the CAP binding site? When is it utilized

Answer 41

this is where the CAP binding protein will bind in the absence of glucose

Question 42

what is the role of the operator? when is it utilzied

Answer 42

in the presence of lactose, the repressor protein bound to the operator will come off and allow transcription in the absence of lactose, the repressor protein will stay on and transcription cannot occur

Question 43

what is the role of the regulatory gene sequence for Lac I

Answer 43

it codes for the repressor protein that will bind to the operator in the presence of lactose

Question 44

what parts of the Lac Operon can come from anywhere in the cell?

Answer 44

the lac repressor and cap binding protein

Question 45

what parts of the Lac Operon only work locally?

Answer 45

the promoter, operator, and cap binding site (regulatory elements)

Question 46

how often is Lac I made?

Answer 46

it is constitutively made and is not regulated

Question 47

how often and where is the CAP binding protein made?

Answer 47

it is constitutively made and is made anywhere in the cytoplasm

Question 48

are the repressor and cap binding proteins always active?

Answer 48

no, they are only active when they bind with effector molecules

Question 49

what is allolactose

Answer 49

it is another form of lactose (made by Beta-galac, need Lac Z) that acts as an effector molecule towards the suppressor

Question 50

when lactose is present, how does the suppressor come off

Answer 50

lactose forms allolactose by beta-galactosidase and is the inducer that causes the suppressor to come off

Question 51

does the repressor bind with lactose to be induced?

Answer 51

no, only allolactose

Question 52

the repressor is senstive to:

Answer 52

lactose only! glucose has NO effect

Question 53

is the repressor on or off? no lactose

Answer 53

on

Question 54

is the repressor on or off yes lactose

Answer 54

off

Question 55

is the CAP activator on or off no glucose

Answer 55

on

Question 56

is the CAP on or off glucose

Answer 56

off

Question 57

the CAP activator protein is sensitive to

Answer 57

glucose only, lactose has no effect

Question 58

how does lactose get into the cell to start lactose metabolism if the transcription of Lac Y is suppressed?

Answer 58

The system is not entirely inhibited, sometimes the repressor comes off and lets lac Y be expressed to let lactose in

Question 59

when the repressor comes off, what is this permissive of?

Answer 59

when the repressor comes off, the RNA polymerase can move through and be transcribed at a very low rate

Question 60

does the repressor completely inhibit transcription

Answer 60

no, some amounts of the enzyme are present still

Question 61

what is a trans acting element

Answer 61

it is a regulatory protein that can regulate genes from any location in a cell

Question 62

what are some examples of trans acting elements

Answer 62

LacI protein and CAP binding protein

Question 63

what is the cis effect

Answer 63

genetic regulation that can only occur next to the gene

Question 64

what is an example of a cis-effect regulation

Answer 64

the promoter, cap binding site, and operator