D2.2 gene expression

Question 1

whats gene expression

Answer 1

process of turning genes on or off meaning genes are accessible for transcription or not

Question 2

how is transcription (gene expression) regulated by proteins

Answer 2

protein attaches to dna near gene to make dna more or less accessible for rna polymerase, increasing or decreasing transcription

Question 3

explain basal transcription factors

Answer 3

this is what always happens during initiation process of transcription

the dna sequence (non coding dna) = the promoter sequence

regulatin binding protein= transcription factors

function= transcription factors bind to promoter sequence of dna forming transcription initiation complex triggering binding of rna polymerase

Question 4

explain how proteins stimulate transcription

Answer 4

this can happen during the initiation process of transcription stimulates more gene expression

dna sequence (non coding dna)= enhancer sequence

regulatory binding protein= activating protein

function=
activator proteins bind to enhancer sequence of dna to greatly increase the rate of transcription of a gene

Question 5

explain how proteins can decrease rate of transcription

Answer 5

this can happen during the innitation process of transcription to decrease gene expression

dna sequence (non coding dna)= silencer sequence

regulatory binding protein= repressor protein

function= repressor protein bind to silencer sequence of dna to either block or reduce the transcription of a gene

Question 6

how do nucleosomes increase gene transcription

Answer 6

when dna loosly wraps itself around histones (euchromatin= liter dna); more transcription genes are turned on

Question 7

how do nucleosomes decrease gene transcription

Answer 7

when dna tightly wraps itself around distone (heterochromatin=darker dna)= no/less transcription because genes are turned off

Question 8

explain acetylation

Answer 8

process of adding an acetly group to histone tail
this promotes transcription
as binds dna more loosly to histone mkaing it more accessible for transcription factors (fomring euchromatin)

Question 9

explain methylation

Answer 9

addition of methyl group to dna
inhibits transcription
binds dna more tightly around histone making it less accessible to transcription factors (fomring heterochromatin)

Question 10

what increases regulation of transcription

Answer 10

increases=
activator protein on the enhancer sequence
addition of acetyl group on histones
wrapping of dna more loosely around histones= euchromatin

Question 11

what decreases regulation of transcription

Answer 11

repressor protein on silencer sequence
addition of methyl group on dna
wrapping dna more tightly around histones= heterochromatin

Question 12

how does the enviornment affect transcription (gene expression) in prokarayotes

Answer 12

enviornmental change= presence of absence of lactose

Question 13

whats P1

Answer 13

attahcment site for RNA polymerase

Question 14

whats lacl

Answer 14

encodes a repressor protein that prevents transcription of the structural genes of the lac operates
makes this repressor protein

Question 15

whats p lac

Answer 15

attachment site for rna polymerase = promoter

Question 16

whats the operator

Answer 16

binding site for the repressor protein

Question 17

lacZ lacY and lacA

Answer 17

encodes for enzymes involved in lactose breakdown

Question 18

what happens with the absence of lactose

Answer 18

lacL which is the regulatory gene makes the repressor protein
this repressor protein binds to the operator, meaning that the rna polymeraze cannot bind to promoter
thus lacZ, lacY and lacA cannot be transcribed and enzymes/ mrna are not made (as there is no necessity to make enzymes which break down lactose if there is no lactose)

Question 19

what happens with the presence of lactose

Answer 19

lacL, the regulatory gene will make the repressor protein,
the repressor protein binds to the operator
however now with presence of lactose, the lactose binds to repressor protein which removes repressor protein from operator
this means that rna polymerase can bind to the promoter and thus transcription can take place making the mrna

Question 20

regulatory gene

Answer 20

dne segment with information for making repressor protein

Question 21

repressor protein + lactose

Answer 21

allows rna polymerase to transcribe structural genes

Question 22

repressor protein without lactose

Answer 22

prevents rna polymerase from attaching to promoter and transcribing structural genes

Question 23

rna polymerase

Answer 23

enzyme that transcribes genes into rna for protein synthesis

Question 24

promoter

Answer 24

location on the operon where rna polymerase starts transcribing genes

Question 25

operator

Answer 25

location on the operon where the repressor protein attaches to prevent transcription

Question 26

operon genes

Answer 26

information for making enzymes that use lactose

Question 27

enzymes

Answer 27

the final products of transcription and translation that use lactose