19.2 controlling gene expression

Question 1

in what ways are genes regulated?

Answer 1

being turned on or off

increasing or decreasing the rate of production

Question 2

why is gene regulation important?

Answer 2

allows for an organism to respond to different changes to the external and internal environments

Question 3

what are the 4 ways of gene regulation?

Answer 3

transcriptional
post-transcriptional
translational
post-translational

Question 4

what is transcriptional regulation?

Answer 4

when a gene is turned on or off

Question 5

what is post-transcriptional regulation?

Answer 5

when the mRNA is modified to regulate translation

Question 6

what is translational regulation?

Answer 6

when translation is tuned on or off

Question 7

what is post-translational regulation?

Answer 7

when proteins are modified after synthesis to change their function

Question 8

what is heterochromatin?

Answer 8

tightly wound DNA which allows DNA to be visible

Question 9

what is euchromatin?

Answer 9

loosely wound DNA which prevents DNA from being visible

Question 10

why cant DNA transcription occur in heterochromatin?

Answer 10

Heterochromatin is too tightly wound for RNA polymerase to operate

therefore transcription of DNA cannot occur

Question 11

can euchromatin be transcribed?

Answer 11

as it is loosely wound, RNA polymerase can operate

therefore transcription occurs

Question 12

how does euchromatin and heterochromatin regulate DNA transcription?

Answer 12

DNA is kept as euchromatin in interphase which allows for transcription

when in cell division, DNA is kept as heterochromatin which prevents transcription

Question 13

why is the regulation of DNA transcription important?

Answer 13

prevents the waste of energy during protein synthesis as transcription is not happening all the time

Question 14

how can histones become more negatively charged?

Answer 14

acetylation (adding acetyl groups)
phosphorylation (adding phosphate)

Question 15

what is the effect of reducing the positive charge of a histone?

Answer 15

causes the DNA to coil less tightly which only allows for certain genes to be transcribed

histone (less positive with addition of acetyl/phosphate) has a weaker attraction to the negative DNA

Question 16

how can histones become more hydrophobic?

Answer 16

methylation (adding a methyl group)

Question 17

what is the effect of making the histones hydrophobic?

Answer 17

causes DNA to coil more tightly which prevents the transcription of genes

Question 18

what is epigenetics?

Answer 18

the control of gene expression by modifying the DNA

Question 19

what is an operon?

Answer 19

group of genes under the control of a regulatory mechanism

Question 20

which organisms mainly have operons?

Answer 20

prokaryotes

Question 21

why are operons useful?

Answer 21

by regulating protein synthesis, operons can save resources when a protein is not needed

Question 22

what is the lac operon composed of?

Answer 22

lacZ
lacY
lacA

Question 23

what is a structural gene?

Answer 23

section of DNA which codes for a protein/enzyme

Question 24

what is a regulatory gene?

Answer 24

section of DNA which codes for a transcription factor

Question 25

what is a transcription factor?

Answer 25

a protein which either switches genes on or off on = activator off = repressor

Question 26

what is the operator?

Answer 26

section of DNA where the transcription factor binds to

Question 27

what is the promoter?

Answer 27

section of DNA where the RNA polymerase binds to

Question 28

what are introns?

Answer 28

non-coding sections of DNA

Question 29

what are exons?

Answer 29

coding sections of DNA which are EXPRESSED

Question 30

how does a transcription factor turn on a gene?

Answer 30

binds to the operator in an operon to cause RNA polymerase to bind to the DNA and activate ACTIVATOR

Question 31

what role do inhibitors play with transcription factors?

Answer 31

they bind to transcription factors and cause a conformational change preventing it from binding to the operator

Question 32

how is the lac operon turned off?

Answer 32

a repressor gene produces a repressor which, when bound to the operator, prevents the binding of RNA polymerase to the DNA at the promoter and thus prevents transcription

Question 33

how is the lac operon turned on?

Answer 33

in the presence of lactose, lactose molecules bind to the repressor causing it to deactivate (by changing it's shape) which stops it binding to the operator and allows RNA polymerase to bind to DNA at the promoter

Question 34

what can increase the rate of transcription of structural genes?

Answer 34

cAMP

Question 35

what does cAMP bind to to increase the rate of transcription?

Answer 35

CRP

Question 36

if glucose and lactose are both present what is metabolised and why?

Answer 36

glucose increase in glucose conc, decreases the cAMP conc which means less transcriptions of genes needed for lactose metabolism

Question 37

what are the two methods of post-transcriptional control?

Answer 37

RNA processing RNA editing

Question 38

what is produced at the end of transcription?

Answer 38

pre-mRNA

Question 39

what is RNA processing?

Answer 39

conversion of pre-mRNA to mature mRNA by splicing

Question 40

what is splicing?

Answer 40

the removal of introns and the joining of exons to produce mature mRNA

Question 41

what is RNA editing?

Answer 41

when the codons are mixed up means that a range of proteins are produced from a single strand of mRNA

Question 42

in what ways is translation controlled?

Answer 42

degradation of mRNA inhibitory proteins initiation factors

Question 43

degradation of mRNA

Answer 43

damaged mRNA molecules cannot bind to the ribosome so translation cannot occur

Question 44

inhibitory proteins

Answer 44

bind to mRNA to prevent it from binding to ribosomes

Question 45

initiation factors

Answer 45

aid mRNA in binding to ribosomes

Question 46

what are protein kinases?

Answer 46

enzymes which catalyse phosphorylation to proteins causes a change in the protein's structure and function

Question 47

what ways is post-translational control carried out?

Answer 47

addition of non-protein groups modifying amino acids folding of proteins modification by cAMP

Question 48

how does cAMP carry out post-transcriptional control?

Answer 48

binds to proteins to change the tertiary structure causing it to activate or deactivate