lecture 19

Question 1

whats the difference between a transcription regulator and a transcription factor

Answer 1

regulator is any molecule that influences transcription in a gene, and a transcription factor is a protein that influences gene transcription

Question 2

what does a gene look like in bacteria

Answer 2

circular, double stranded

Question 3

define operons

Answer 3

genes involved in same biological process often grouped

Question 4

what is a cluster of genes transcribed to one mRNA

Answer 4

polycistronic mRNA

Question 5

do eukaryotes have polycistronic RNA

Answer 5

no

Question 6

what are the 5 parts of an operon

Answer 6

structural gene
promotor
operator
regulatory gene
transcription regulator

Question 7

what are the actual genes that we are transcribing

Answer 7

structural genes in operon

Question 8

what kind of operon is the Trp operon

Answer 8

repressible operon

Question 9

what does a Trp operon repress

Answer 9

transcription

Question 10

what does the Trp operon require to bind to operator

Answer 10

corepressor (tryptophan)

Question 11

where do Trp operons bind

Answer 11

the operator

Question 12

what is the active Trp operon

Answer 12

it is bound to the operator with tryptophan and is stopping transcription of more tryptophan

Question 13

what is the inactive Trp operon

Answer 13

it is not bound to the operator and does not have a tryptophan molecule bound to it. transcription of tryptophan is occurring

Question 14

when is Trp operon active (lots or no tryptophan)

Answer 14

when there is lots of tryptophan

Question 15

when is Trp operon inactive (lots or no tryptophan)

Answer 15

no tryptophan so more needs to be transcribed

Question 16

what cell has Trp operon and Lac operon

Answer 16

bacteria

Question 17

what is a Lac operon involved in

Answer 17

breaking down lactose

Question 18

what kind of operon is a Lac operon

Answer 18

inducible operon

Question 19

what is an inducer operon

Answer 19

an operon that is turned on in the presence of an inducer

Question 20

what is an active Lac operon

Answer 20

it has no lactose molecule bound to it so it binds and blocks transcription

Question 21

what is an inactive Lac operon

Answer 21

it has a lactose molecule bound to it that inactivates it so enzymes are transcribed that can break down lactose

Question 22

why do cell types in eukaryotes have different functions

Answer 22

because we regulate which genes are expressed in a particular cell type

Question 23

what are genes in eukaryotes turned on and off by

Answer 23

regulatory proteins

Question 24

does each cell type have the same DNA but unique set of proteins in eukaryotes

Answer 24

yes

Question 25

what are the 4 level of gene expression

Answer 25

transcriptional control processing control translational control post translational control

Question 26

what are the two gene expressions that occur in the nucleus

Answer 26

transcriptional control processing control

Question 27

what are the two gene expressions that occur in the cytoplasm

Answer 27

translational control post translational control

Question 28

what is transcriptional control

Answer 28

controls wether of not the genes are transcribed

Question 29

what is processing control

Answer 29

modifications at the pre mRNA level

Question 30

what is translational control

Answer 30

controls wether or not th ribosome actually translates RNA into polypeptide or not

Question 31

what is post translational control

Answer 31

after translation has happened and expression is being controlled

Question 32

what are the 5 types of transcriptional control

Answer 32

differential transcription transcription regulators regulation of chromatin structure paused polymerase transcriptional repression

Question 33

what is 1. differential transcription

Answer 33

regulation of which genes are transcribed into RNA (embryonic, tissues)

Question 34

what is the 2. transcription regulator in transcriptional control

Answer 34

enhancers - DNA elements that increase transcriptional rate

Question 35

what are characteristics of enhancers (3)

Answer 35

usually located far away upstream or downstream can be inverted

Question 36

how are enhancers different from promotors

Answer 36

enhancers are not directionally specific like promoters are

Question 37

how does an enhancer work from so far away

Answer 37

it loops over itself

Question 38

what brings the enhancer and the transcription region together

Answer 38

mediator protein complex

Question 39

what is the 3. regulation of chromatin structure for

Answer 39

changes in the nucleosomes/chromatin structure allowing access to the DNA

Question 40

what remodels chromatin

Answer 40

chromatin remodling complex

Question 41

what does the chromatin remodling complex do

Answer 41

it changes position of the nucleosome by disrupting the histone-DNA interactions

Question 42

what is easier to access DNA (tight or loose)

Answer 42

loose

Question 43

what does moving position of core histone complex require (2)

Answer 43

chromatin remodelling complex ATP

Question 44

what is histone dissociation

Answer 44

DNA completely removed from histone and re associated

Question 45

what are the (2) 3. regulation of chromatin structure systems

Answer 45

chromatin remodelling complex histone modifying enzymes

Question 46

what do histone modifying enzymes do

Answer 46

covalently modify the core histone protein tails

Question 47

what would the acetylation of lysine (K9) do to a histone tail

Answer 47

loosen the chromatin structure by affecting affinity for other tails

Question 48

what histone tail is heavily modified

Answer 48

H3

Question 49

what would the trimethylation of lysine (K9) do to a histone tail

Answer 49

compact it and silence the gene

Question 50

what molecules are used in histone tail modification (3)

Answer 50

acetyl, methyl and phosphate groups

Question 51

whats 4. paused polymerase

Answer 51

RNA polymerase bound to promoters of many genes but show no evidence that they are being transcribed

Question 52

where can a polymerase be paused

Answer 52

after initiation and right before elongation of transcription

Question 53

RNA polymerase situated where may be held in the paused state

Answer 53

downstream of promoters

Question 54

what are the (3) 5. transcriptional repression mechanisms

Answer 54

deacetylation DNA methylation Long noncoding RNAs (LncRNA)

Question 55

what is deacetylation in transcriptional repression

Answer 55

histone deacetylases remove acetyl groups -> repress transcription

Question 56

what is DNA methylation in transcriptional repression

Answer 56

DNA methyltransferases remove methyl group from the C5 of cytosine

Question 57

which transcriptional repressor is important during embryonic development

Answer 57

DNA methylation

Question 58

what are LncRNAs most associated with ? whats an example of it

Answer 58

gene repression (Xist- x chromsome inactivation)

Question 59

what are the 2 forms of processing control

Answer 59

alternative splicing sequence specific nucleus export

Question 60

what is alternative splicing ? what does it allow ?

Answer 60

intron removal allows for multiple proteins to be synthesized on the same gene

Question 61

whats an intervening sequence

Answer 61

an intron (non coding)

Question 62

whats an expressed sequence

Answer 62

exon (coding)

Question 63

do mature mRNA have intervening sequences

Answer 63

no

Question 64

what are split genes

Answer 64

parts with a coding portion and a noncoding portion

Question 65

what increases protein diversity in a single gene

Answer 65

RNA splicing

Question 66

how does the cell know the difference between introns and exons

Answer 66

special sequences within introns act as cues for splicing machinery