Block A 2

Question 1

what is supercoiled DNA

Answer 1

when DNA is further twisted to save space

Question 2

negative supercoiling

Answer 2

double helix is underwound

Question 3

positive supercoiling

Answer 3

double helix is overwound

Question 4

relaxed DNA

Answer 4

DNA has number of turns predicted by number of base pairs

Question 5

where is negative supercoiling predominately found

Answer 5

in nature

Question 6

what catalyses DNA supercoiling

Answer 6

DNA gyrase

Question 7

difference between RNA and DNA genomes

Answer 7

linear or circular
single or double stranded

Question 8

how do plasmids replicate

Answer 8

separately from chromosome

Question 9

what does pNDM plasmid encode and confer

Answer 9

new dehli beta lactamase
resistance to beta lactam antibiotics

Question 10

what is a chromosome

Answer 10

large, encodes all essential genes and more

Question 11

what are plasmids

Answer 11

small, many copies, non essential but advantageous genes (antibiotic resistance)

Question 12

what are transposable elements

Answer 12

segment of DNA that can move from one site to another site on the same or different DNA mol

Question 13

3 main types of transposable elements

Answer 13

insertion sequences
transposons
special viruses

Question 14

what do sigma factors recognise

Answer 14

two highly conserved regions of promoter

Question 15

what are the 2 conserved regions

Answer 15

pribnow box- 10 bases before start of transcription (-10 region)
-35 region- -35 bases upstream of transcription

Question 16

how do sigma factors govern promoter recogniton

Answer 16

RNAP

Question 17

what is a unit of transcription

Answer 17

unit of chr bounded by sites where transcription of DNA to RNA is initiated and terminated

Question 18

3 types of rRNA

Answer 18

16S
23S
5S

Question 19

half life of mRNAs

Answer 19

short
(few mins)

Question 20

polycistronic mRNA

Answer 20

an mRNA encoding group of cotranscribed genes

Question 21

operon

Answer 21

group of related genes cotranscribed on a polycistronic mRNA
allows for expression of multiple genes to be coordinated

Question 22

homodimeric proteins

Answer 22

proteins composed of 2 identical proteins

Question 23

why do mRNA transcripts have a short half life

Answer 23

prevents production of unneeded proteins

Question 24

what do protein dimers interact with on DNA

Answer 24

inverted repeats

Question 25

DNA binding proteins interact with DNA is a sequence-specific manner, how is specificity achieved

Answer 25

by interactions between aa side chains and chem groups on bases and sugar phosphate backbone

Question 26

what is the main site of protein binding

Answer 26

major groove of DNA

Question 27

3 possible outcomes after DNA binding

Answer 27

-DNA binding protein may catalyse a specific reaction on the DNA mol -negative regulation -positive regulation

Question 28

what is negative regulation

Answer 28

binding event can block transcription

Question 29

what is positive regulation

Answer 29

binding event can activate transcription

Question 30

inducer

Answer 30

substance that induces enzyme synthesis

Question 31

corepressor

Answer 31

substance that represses enzyme synthesis

Question 32

effectors

Answer 32

collective term for inducers and repressors affect transcription indirectly by binding to specific DNA binding proteins

Question 33

what do repressor molecules bind to

Answer 33

allosteric repressor protein

Question 34

once allosteric repressor becomes active where does it bind

Answer 34

region of DNA near promoter operator

Question 35

operon

Answer 35

cluster of genes arranged in a linear fashion whose expression is under control of a cingle operator

Question 36

what is physically blocked when repressor binds to operator

Answer 36

transcription

Question 37

what else can be controlled by a repressor

Answer 37

enzyme induction

Question 38

what is negative control

Answer 38

a regulatory mechanism that stops transcription

Question 39

what is repression

Answer 39

preventing synthesis of an enzyme in response to a signal

Question 40

what type of enzyme does repression normally affect

Answer 40

anabolic enzymes eg arginine biosynthesis

Question 41

what is positive control

Answer 41

regulator protein activates binding of RNA polymerase to DNA

Question 42

what is the DNA sequence that activator proteins bind to called

Answer 42

activator binding site

Question 43

what must first occur so maltose activator protein can bind to DNA

Answer 43

must first bind maltose

Question 44

binding strength of promoters of positively controlled operons to RNA pol

Answer 44

weak

Question 45

what does activator protein help RNA pol do

Answer 45

recognise promoter

Question 46

what can be said about distance of activator binding site and promoter

Answer 46

may be close or several hundred base pairs away

Question 47

name given to multiple operons controlled by the same regulatory protein

Answer 47

regulon

Question 48

what are global control systems

Answer 48

regulate expression of many different genes simultaneously

Question 49

example of global control

Answer 49

catabolite repression

Question 50

what is diauxic growth

Answer 50

2 exponential growth phases

Question 51

what is the activator protein used to control transcription in catabolite repression

Answer 51

cyclic AMP receptor protein (CRP)

Question 52

what is a key mol in many metabolic control systems (regulatory nucleotide)

Answer 52

cyclic AMP

Question 53

what other genes also controlled by catabolite repression

Answer 53

flagellar genes (no need to swim in search of nutrients)

Question 54

prokaryotes regulate cellular metabolism in response to

Answer 54

environmental fluctuations

Question 55

what is signal transduction

Answer 55

external signal detected by senor and transmitted to regulatory machinery

Question 56

what are the 2 components in the 2 component regulatory system

Answer 56

sensor kinases response regulator

Question 57

what and where is sensor kinases

Answer 57

in cytoplasmic membrane detects environmental signal and autophosphorylates

Question 58

what is where is response regulator

Answer 58

in cytoplasm DNA binding protein that regulates transcription

Question 59

chemotaxis used to

Answer 59

sense temporal changes in attractants or repellants regulate flagellar rotation

Question 60

3 main steps of chemotaxi regulation

Answer 60

response to signal controlling flagellar rotation adaptation

Question 61

what do MCPs do in response to signal (chemotaxi)

Answer 61

bind attractant or repellant and initate flagellar rotation

Question 62

what is flagellar rotation controlled by (chemotaxi)

Answer 62

CheY protein

Question 63

what method of adaptation used (chemotaxi)

Answer 63

feedback loop

Question 64

phototaxis

Answer 64

movement toward light light sensors replace MCPs

Question 65

aerotaxis

Answer 65

movement toward oxygen redox protein monitors oxygen level

Question 66

what is quorum sensing

Answer 66

mechanism by which bacteria assess their pop. density

Question 67

what does each species of bacterium produce

Answer 67

specific autoinducer

Question 68

what do autoinducers do

Answer 68

bind to specific activator protein and triggers transcription of specific genes

Question 69

what was first autoinducer identified

Answer 69

AHL acyl homoserine lactone

Question 70

what encodes bioluminescence

Answer 70

lux operon

Question 71

examples of quorum sensing

Answer 71

virulence factors switching from free living to growing as biofilm