c) Lactose present, glucose present:
Lactose taken up at slow rate by small amount of permease present in the cell.
Some lactose turned into allolactose.
Allolactose binds to repressor which loses its affinity for the operator.
Glucose high, cAMP low 
 CAP cannot bind to CAP site
RNA polymerase binds  and a modest level of transcription takes place.
d) Lactose present, glucose absent:
Lactose taken up at slow rate by small amount of permease present in the cell.
Some lactose turned into allolactose.
Allolactose binds to repressor which loses its affinity for the operator.
Glucose low, cAMP high 
 CAP-cAMP complex binds to CAP site.
RNA polymerase binds readily to the promoter and a high level of transcription takes place. 
16 of  30
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FirstPage
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1st Page
"textgo"
"text1"
--Repressor already present on DNA
--RNA polymerase moves 
"RNApol" 
)-1095, 510
-1080, 420
-1005, 435
-945, 435
-900, 480
-825, 510
-765, 525
-675, 630
-585, 705
-465, 780
-315, 855
-150, 1020
0, 1230
240, 1485
615, 1485
990, 1485
1485, 1485
"text2"
--2 allolactose molecules (al1,al4) 
holes 
repressor
)4326, 510
3906, 675
3471, 825
2886, 990
2436, 1275
)4540, 421
4030, 676
3505, 931
3250, 
"al4" 
2796, 1485
, al1 
! hidden 
replaced 
Hrep2
--Rep2 
square 
es bound (al5,al8) 
same 
--positions 
C= rep1b (
$empty) + 
)2265, 1095
off DNA
2340, 1050
2415, 1005
2475, 945
--Remaining 2 
es (al6,al7) join 
)3831, -84
3801, 81
3696, 321
3576, 576
3306, 786
2991, 1056
)3366, -84
3156, 306
3006, 471
2736, 771
2646, 1281
es grouped together so can 
%1 unit
+ al6 + al7 = rep3
Group
--Rep3 moved 
screen
2340, 1050
2415, 1005
2475, 945
2580, 885
2700, 810
2790, 750
2865, 675
2955, 585
3015, 495
3195, 405
3390, 315
"text3"
"text4"
--Open complex (
trans) shown, 
Shalf 
)1935, 1615
"leftrans"
240, 75.125, 100
240, 75.125, 100
"rightrans"
0, 75.3125, 0
0, 75.6875, 0
"text5"
--Abortive initiation strans 
ungrouped 
s (sigma 
rna-s
--(core enzyme). Sigma 
 dissociates 
leaves.
!"ab1" 
)1785, 2070
795, 2480
!"ab2" 
)1785, 2070
950, 2750
!"ab3" 
)1785, 2070
585, 2655
Ungroup
1275, 1305
1185, 1215
1125, 1155
1065, 1065
1005, 1035
930, 945
885, 870
840, 795
780, 705
630, 480
525, 405
330, 285
105, 165
-105, 75
-315, -15
630, 480
!"pa"
"text6"
--Elongation starts-
mRNA strand (
pa-po) 
--Core 
nalong 1 
--Each 
Qcolour
!"pa"
2235, 1455
0, 75.3125, 0
0, 75.3125, 0
120, 75.125, 100
120, 75.125, 100
2295, 1645
2610, 1455
120, 75.125, 100
120, 75.125, 100
60, 87.625, 100
60, 87.625, 100
2670, 1645
"pc" 
2985, 1455
60, 87.625, 100
60, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3060, 1645
"pd" 
3345, 1455
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3420, 1645
"pe" 
3720, 1455
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3810, 1645
"pf" 
4080, 1455
0, 87.625, 100
0, 87.625, 100
60, 87.625, 100
60, 87.625,100
4185, 1645
"pg" 
4500, 1455
60, 87.625, 100
60, 87.625, 100
180, 87.625, 100 
180, 87.625, 100
4575, 1645
"ph" 
4845, 1455
180, 87.625, 100 
180, 87.625, 100
180, 87.625, 100 
180, 87.625, 100
4965, 1645
5280, 1455
180, 87.625, 100 
180, 87.625, 100
60, 87.625, 100 
60, 87.625, 100
5325, 1645
"pj" 
5610, 1455
60, 87.625, 100 
60, 87.625, 100
0, 75.125, 100 
0, 75.125, 100
5700, 1645
"pk" 
6015, 1455
0, 75.125, 100 
0, 75.125, 100
0, 75.125, 100 
0, 75.125, 100
6090, 1645
"pl" 
6360, 1455
0, 75.125, 100 
0, 75.125, 100
60, 87.625, 100 
60, 87.625, 100
6450, 1645
"pm" 
"text7"
6750, 1455
60, 87.625, 100
60, 87.625, 100
60, 87.625, 100 
60, 87.625, 100
6840, 1645
"pn" 
--Last 
Hlinear 
"po" 
renamed
loses 
). This 
xseen on 
990, 120
"text8"
"text9"
leaving 
es al5-al6.
--Allolactose 
"al7"
3441, 591
3396, 471
3381, 351
3351, 246
3321, 126
3306, 66
3291, -9
3276, -84
"al6"
3921, 381
3921, 336
3921, 291
3951, 276
3951, 246
3966, 216
3981, 156
3981, 111
4011, 81
4011, 36
4011, -9
4011, -24
4011, -84
 al5 
--Rep1b 
Hrep 
al4 which 
form rep4
3591, 366
)3408, 321
--Rep4 
where 
"al5" 
3606, 306
3636, 231
3636, 186
3636, 111
3636, 66
3636, 36
3636, -24
3636, -69
3348, 426
3258, 516
3108, 591
3033, 636
2898, 696
2763, 771
2673, 831
2538, 921
2463, 981
2373, 1086
2313, 1146
2283, 1161
2916, 1476
3066, 1401
3186, 1296
3381, 1131
3546, 876
3636, 666
3741, 456
3831, 261
3921, 126
3951, -69
--re1b, 
reform 
)3390, 315
"al8"
3561, 426
3891, 651
--Text fields 
default 
buttonUp
7buttonUp
textgo
text1
RNApol
RNApol
text2
Group
text3
text4
leftrans
leftrans
leftrans
rightrans
rightrans
rightrans
text5
RNApol
WUngroup
text6
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
text7
rna-s
leftrans
leftrans
rightrans
rightrans
trans
trans
rna-s
Group
RNApol
RNApol
text8
text9
WUngroup
WUngroup
rep1b
Group
WUngroup
rep1b
rep1b
Group
text1
text2
text3
text4
text5
text6
text7
text8
text9
textgo
default
trans
Basic
AIMS AND OBJECTIVES
      
      2.         g animations the significant features of haemostasis
      2.         tudents in their first or second years.
      1. To illustrate using animations the significant features of haemostasis
      2.               1. To illustrate using animations the significant features of haemostasis
      2.         
This program is intended for use by students in their first or second year taking Biochemistry as part of their course. The program makes use of animations to illustrate the dynamic aspects of the control of transcription in prokaryotes. The aims and objectives are as follows:
1. To show the elements of the lac operon involved in transcription control.
     
2. To illustrate the process of transcription and the repressor-mediated 
    control imposed by the presence or absence of lactose.
3. To illustrate additional control exerted through catabolite activator protein 
   (CAP) under the influence of glucose concentration.
4. To test your understanding of the tutorial by means of a multiple-choice 
    quiz.iple-choice 
    quiz..
    quiz.ultiple-choice 
    quiz.ple-choice 
    quiz.
ExitProgram
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FirstPage
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1st Page
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Previous
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--removes cross 
the answer boxes
"quest1" 
"quest2" 
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quest1
quest2
quest1
2. RNA polymerase binds to ::::
The operator
The repressor
The promoter
The CAP site
Allolactose
quest2
NextPage
--see 
--questscore1 
question 1. It 
zero 
Fincreases
decreases depending on which answer boxes are 
--same applies 
questscores 2-20
--checkboxes 
6labelled a-z 
Fa1-z1 
Fa2-z2 etc (could have been 
/better)
--All forthcoming 
fquestions on 
layout except 
4questscore2
B"a" 
B"b" 
B"c" 
B"d" 
B"e" 
B"f" 
B"g" 
B"h" 
B"i" 
B"j" 
default
buttonUp
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default
questscore2
questscore1
1. Which genes are controlled by the Lac Operon ::
b-galactosidase
Lactate dehydrogenase
Lactose Transacetylase
Lactose Permease
Lac repressor
18 of  30
"quest11" 
"quest12" 
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quest11
quest12
NextPage
4questscore11
4questscore12
B"y1" 
B"z1" 
B"a2" 
B"b2" 
B"c2" 
B"d2" 
B"e2" 
B"f2" 
B"g2" 
B"h2" 
default
buttonUp
buttonUp
default
questscore12
questscore11
11. The CAP site binds :::::::::
CAP-cAMP complex
Catabolite Activator Protein
RNA polymerase
Lactose-repressor complex
Allolactose-repressor complex
quest11
quest12
12. Lactose has which conformation :
Gluc b(1
4) Gal
Gal b(1
4) Gluc
Gluc a(1
4) Gal
Gal  b(1
6) Gluc
Gluc  b(1
6) Gal
23 of  30
"quest13" 
"quest14" 
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quest13
quest14
NextPage
4questscore13
4questscore14
B"i2" 
B"j2" 
B"k2" 
B"l2" 
B"m2" 
B"n2" 
B"o2" 
B"p2" 
B"q2" 
B"r2" 
default
buttonUp
buttonUp
default
questscore14
questscore13
quest13
quest14
13. Which of the following are inducers? ::
Allolactose
Lactose
Glucose
Galactose
Cyclic AMP
14. Dissociation constant of the repressor-operator complex is about :
24 of  30
"quest15" 
"quest16" 
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quest15
quest16
NextPage
4questscore15
4questscore16
B"s2" 
B"t2" 
B"u2" 
B"v2" 
B"w2" 
B"x2" 
B"y2" 
B"z2" 
B"a3" 
B"b3" 
default
buttonUp
buttonUp
default
questscore16
questscore15
quest15
quest16
15. The repressor molecule is a  ::::::::::
Monomer
Dimer
Trimer
Tetramer
Pentamer
16. Function of b-galactosidase ::
To allow entry of lactose into cell
Breakdown of lactose into glucose + mannose
To allow lactose to be used as a carbon source
Breakdown of lactose into glucose + galactose
To allow lactose to be used as an energy sourceM
25 of  30
"quest17" 
"quest18" 
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quest17
quest18
NextPage
4questscore17
4questscore18
B"c3" 
B"d3" 
B"e3" 
B"f3" 
B"g3" 
B"h3" 
B"i3" 
B"j3" 
B"k3" 
B"l3" 
default
buttonUp
buttonUp
default
questscore18
questscore17
quest17
quest18
17. The Catabolite Activator Protein is a  :
Monomer
Dimer
Trimer
Tetramer
Pentamer
18 Maximum number of molecules of allolactose repressor can bind is  :
26 of  30
B"NextPage"
"quest19" 
"quest20" 
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NextPage
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quest19
quest20
NextPage
4questscore19
4questscore20
buttonUp
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questscore20
questscore19
quest19
quest20
19. Maximum number of molecules of cyclic AMP CAP can bind is  :is  ::
20. Which of the following DNA sequences exhibit a two fold axis of symmetry  :
Promoter
Operator
CAP site
b-galactosidase gene
Permease geneeeeeeeeeeeeeeee
Score
Press the 'Score' button after finshing the questions to obtain your final score.  
27 of  30
4questscore19
4questscore20
B"m3" 
B"n3" 
B"o3" 
B"p3" 
B"q3" 
B"r3" 
B"s3" 
B"t3" 
B"u3" 
B"v3" 
4questscore18
4questscore17
4questscore16
4questscore15
4questscore14
4questscore13
4questscore12
4questscore11
4questscore10
4questscore9
4questscore8
4questscore7
4questscore6
4questscore5
4questscore4
4questscore3
--System count 
questscores
--Obtain dialog box showing total no 
points	
"You scored" && 
 out 
a possible 100"
--shows nextpage 
B- avoids 
Bbeing pressed without 
--obtaining 
B"NextPage"
default
buttonUp
buttonUp
You scored
points out of a possible 100
NextPage
default
count
questscore1
questscore2
questscore3
questscore4
questscore5
questscore6
questscore7
questscore8
questscore9
questscore10
questscore11
questscore12
questscore13
questscore14
questscore15
questscore16
questscore17
questscore18
questscore20
questscore19
"textgo"
"text0.5"
--RNA polymerase goes 
moves 
forth 
Zpromoter
--region 
reached
"RNApol" 
)-1150, 480
ZhorizPos
nthe 
-1080, 420
-1005, 435
-945, 435
-900, 480
-825, 510
-765, 525
-675, 630
-585, 705
-465, 780
-315, 855
-150, 1020
0, 1230
240, 1485
6615 
, 1485
6615 
-135 
H-750
, 1485 
-135 
6615 
, 1485
6615 
-135 
H-375
, 1485 
240, 1485
615, 1485
990, 1485
1485, 1485
"text1"
--Open complex (
trans) appears 
half coloured 
)1890, 1645
"leftrans"
240, 75.125, 100
240, 75.125, 100
"rightrans"
0, 75.3125, 0
0, 75.6875, 0
--Abortive initiation takes place, releasing strands 
(ab1-ab3)
--Sigma unit
s) dissociates
)1785, 2070
795, 2480
!"ab2" 
)1785, 2070
1055, 2655
)1785, 2070
585, 2655
Ungroup
1275, 1305
1185, 1215
1125, 1155
1065, 1065
1005, 1035
930, 945
885, 870
840, 795
780, 705
630, 480
525, 405
330, 285
105, 165
-105, 75
-315, -15
630, 480
!"pa"
"text3"
--Elongation starts - 
mRNA 
 (pa-po)hidden
--Core enzyme (
rna-s) 
along DNA
hanging 
!"pa"
2235, 1455
0, 75.3125, 0
0, 75.3125, 0
120, 75.125, 100
120, 75.125, 100
2280, 1645
!"ab1"
!"ab3"
2610, 1455
120, 75.125, 100
120, 75.125, 100
60, 87.625, 100
60, 87.625, 100
2655, 1645
"pc" 
2985, 1455
60, 87.625, 100
60, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3030, 1645
"pd" 
3345, 1455
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3420, 1645
"pe" 
3720, 1455
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3780, 1645
"pf" 
4080, 1455
0, 87.625, 100
0, 87.625, 100
60, 87.625, 100
60, 87.625,100
4155, 1645
"pg" 
4500, 1455
60, 87.625, 100
60, 87.625, 100
180, 87.625, 100 
180, 87.625, 100
4560, 1645
"ph" 
4845, 1455
180, 87.625, 100 
180, 87.625, 100
180, 87.625, 100 
180, 87.625, 100
4920, 1645
5280, 1455
180, 87.625, 100 
180, 87.625, 100
60, 87.625, 100 
60, 87.625, 100
5325, 1645
"pj" 
5610, 1455
60, 87.625, 100 
60, 87.625, 100
0, 75.125, 100 
0, 75.125, 100
5685, 1645
"pk" 
6015, 1455
0, 75.125, 100 
0, 75.125, 100
0, 75.125, 100 
0, 75.125, 100
6060, 1645
"pl" 
6360, 1455
0, 75.125, 100 
0, 75.125, 100
60, 87.625, 100 
60, 87.625, 100
6420, 1645
"pm" 
"text4"
6750, 1455
60, 87.625, 100
60, 87.625, 100
60, 87.625, 100 
60, 87.625, 100
6810, 1645
"pn" 
--Straight piece 
po) shown
moved 
sigma 
grouped together
"po" 
990, 120
Group
--Text fields 
"text5"
"text2"
sysLockscreen 
default
buttonUp
#buttonUp
textgo
text0.5
RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
text1
leftrans
leftrans
leftrans
rightrans
rightrans
rightrans
RNApol
WUngroup
text3
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
text4
rna-s
leftrans
leftrans
rightrans
rightrans
trans
trans
rna-s
Group
RNApol
RNApol
text5
textgo
text0.5
text1
text2
text3
text4
text5
default
trans
horizPos:by
horizPos:to
horizPos
"textgo"
leavePage
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textgo
"D$N(
ChE4F
H2JxN
QHQ0S`S
URV6W
RNApol
rna-s
o	B	"
!"ab3"
buttonUp
buttonUp
!"ab2"
buttonUp
buttonUp
!"ab1"
buttonUp
buttonUp
Press the "Animate" button
buttonUp
buttonUp
!"pa"
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
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buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
buttonUp
text1
"text1"
buttonUp
buttonUp
text1
Cyclic AMP binds to the CAP to form the CAP-cAMP complex. This then binds to the CAP siteeeeore readily.
text1a
"text1a"
buttonUp
buttonUp
text1a
The RNA polymerase binds to the DNA and moves along the DNA until it reaches the promoter
text1b
"text1b"
buttonUp
buttonUp
text1b
When the RNA polymerase reaches the promoter the CAP-cAMP complex interacts with the RNA polymerase increasing the probability that the RNA polymerase will bind to the promoter. The repressor also increases this probability.
text2
"text2"
buttonUp
buttonUp
text2
Allolactose binds to the repressor causing a conformational change which results in the repressor leaving the operator.
text3
"text3"
buttonUp
buttonUp
text3
RNA polymerase free to carry out transcription.ormational change which results in the repressor leaving the operator.
text4
"text4"
buttonUp
buttonUp
text4
RNA polymerase binds then melts a section of DNA into single strands to form  the open complex.
text5
"text5"
buttonUp
buttonUp
text5
Abortive initiation occurs until the sigma unit dissociates and the core enzyme can move along the DNA.
text6
"text6"
buttonUp
buttonUp
text6
Elongation   binds to DNA, melts a section into single strands to form open complex.
text7
"text7"
buttonUp
buttonUp
text7
Termination
binds to DNA, melts a section into single strands to form open complex.
text8
"text8"
buttonUp
buttonUp
text8
Strand of mRNA formed
text9
"text9"
buttonUp
buttonUp
text9
Once the lactose concentration decreases, the repressor can once more bind to the operator. The CAP-cAMP complex will remain on the CAP site until the glucose concentration increases...
textgo
"textgo"
buttonUp
buttonUp
textgo
REPEAT OR MOVE ON TO THE NEXT PAGEEE
Allolactose
Cyclic AMP
\B4BYB
Allolactose binding site
14 of  30
Button
d) Events when Lactose present & Glucose 			     concentration loww
XE0EUE
& Glucose concentration low
camp1
"camp1"
buttonUp
buttonUp
camp1
"cap"
buttonUp
buttonUp
camp2
"camp2"
buttonUp
buttonUp
camp2
cap-camp
trans
	3	.P
intrans
"trans"
buttonUp
buttonUp
trans
rightrans
	3	|P
leftrans
outrans
Animate2
Animate
rep1b
"al4"
buttonUp
buttonUp
"al1"
buttonUp
buttonUp
backPage
Previous
default
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Previous
default
NextPage
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SysSuspendMessages 
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FirstPage
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1st Page
Buttons Used In The Following Pagess
ExitProgram
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FirstPage
1st Page
Move to the next page
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Return to the first page of 
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Animate
Animate
Animates the sequence of events on that page
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barchart
X"k"o"
"textgo"
"cap-camp"
"text1"
--CAP moves 
screen
--2 molecules 
cyclic AMP (camp1,camp2) appear 
binding sites
1 are hidden 
be replaced 
-cAMP complex (
), which 
)-630, 2880
-495, 2790
-285, 2640
-105, 2520
90, 2370
270, 2280
405, 2190
)-90, 3525
15, 3465
120, 3360
195, 3270
255, 3150
345, 3000
405, 2895
480, 2805
570, 2625
)-75, 3390
60, 3315
180, 3210
330, 3090
465, 2955
630, 2835
765, 2760
810, 2625
"cap"
)400, 2180
505, 2165
625, 2135
805, 2090
940, 2075
1075, 2045
1240, 2000
1375, 1955
1495, 1895
1525, 1805
"text1a"
--RNA polymerase enters 
"RNApol" 
)8430, 165
8295, 255
8130, 345
7890, 495
7785, 540
7665, 585
7500, 645
7380, 690
7170, 795
7005, 915
6840, 1035
6630, 1230
6510, 1320
6450, 1350
6360, 1440
down 
Hsteps 
horizPos 
6360 
3735 
H-375
", 1440
3735 
6735 
L, 1440
leaves 
exits 
6885, 1320
7095, 1200
7320, 1110
7470, 1050
7680, 945
7890, 825
8085, 720
8325, 585
"text1b"
promoter
)-975, 510
-855, 525
-660, 630
-450, 645
-180, 705
60, 705
345, 765
705, 810
1140, 930
1470, 1020
2220, 1455
"text2"
--Allolactose 
repressor
)4326, 510
3966, -90
3861, 60
3771, 195
3651, 315
3531, 495
3411, 705
3276, 885
3186, 1005
3156, 1275
)4941, -90
4941, -90
"al4" 
4911, 45
4836, 255
4746, 435
4626, 600
4476, 780
4311, 945
4131, 1095
3936, 1275
3516, 1485
 + 2 allolactose 
Hrep2.
--Rep2 
square 
 consisting 
rep1b 
"al1"
)2985, 1050
	off DNA
--2 remaining 
	(al6,al7) 
3045, 1050
3135, 990
3225, 960
)4611, -84
4551, 126
4431, 276
4311, 441
4086, 711
3741, 1071
)5286, -69
5031, 141
4716, 441
4371, 606
4116, 801
3396, 1296
grouped 
fal6 
form rep3
Group
--Rep3 
3330, 840
3420, 780
3525, 705
3645, 615
3690, 570
3795, 465
3900, 300
3960, 240
3975, 180
"text3"
"text4"
--Open 
appears (
Hmajic)
trans 
)2655, 1615
"leftrans" 
240, 75.125, 100
240, 75.125, 100
"rightrans" 
0, 75.3125, 0
0, 75.6875, 0
"text5"
--Abortive initiation strands (ab1-ab3) shown
)2630, 2060
2415, 2195
2220, 2330
2025, 2450
1965, 2525
!"ab2" 
)2630, 2060
2615, 2210
2540, 2375
2375, 2570
)2630, 2060
!"ab3"
2490, 2250
2415, 2370
ungrouped - gives sigma unit (
core enzyme
rna-s)
--Sigma 
Ungroup
2190, 1665
2190, 1530
2100, 1395
1965, 1275
1770, 1125
1590, 1005
1410, 915
1125, 780
900, 720
600, 630
360, 540
150, 465
-15, 375
-150, 285
-285, 195
630, 480
!"pa"
"text6"
--Elongation begins (see scripts 
events (a) 
!"pa"
2940, 1455
0, 75.3125, 0
0, 75.3125, 0
120, 75.125, 100
120, 75.125, 100
3015, 1615
!"ab1"
3330, 1455
120, 75.125, 100
120, 75.125, 100
60, 87.625, 100
60, 87.625, 100
3390, 1615
"pc" 
3720, 1455
60, 87.625, 100
60, 87.625, 100
0, 87.625, 100
0, 87.625, 100
3765, 1615
"pd" 
4095, 1455
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
4140, 1615
"pe" 
4455, 1455
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
0, 87.625, 100
4515, 1615
"pf" 
4830, 1455
0, 87.625, 100
0, 87.625, 100
60, 87.625, 100
60, 87.625,100
4905, 1615
"pg" 
5205, 1455
60, 87.625, 100
60, 87.625, 100
180, 87.625, 100 
180, 87.625, 100
5310, 1615
"ph" 
5595, 1455
180, 87.625, 100 
180, 87.625, 100
180, 87.625, 100 
180, 87.625, 100
5670, 1615
5970, 1455
180, 87.625, 100 
180, 87.625, 100
60, 87.625, 100 
60, 87.625, 100
6045, 1615
"pj" 
6345, 1455
60, 87.625, 100 
60, 87.625, 100
0, 75.125, 100 
0, 75.125, 100
6435, 1615
"pk" 
6735, 1455
0, 75.125, 100 
0, 75.125, 100
0, 75.125, 100 
0, 75.125, 100
6825, 1615
"pl" 
7095, 1455
0, 75.125, 100 
0, 75.125, 100
60, 87.625, 100 
60, 87.625, 100
7170, 1615
"pm" 
"text7"
7455, 1455
60, 87.625, 100
60, 87.625, 100
60, 87.625, 100 
60, 87.625, 100
7545, 1615
"pn" 
"po" 
--Core 
 moved 
together
990, 120
"text8"
"text9"
, al5-al8
"al7"
4026, 516
3891, 441
3846, 336
3786, 231
3786, 111
3786, 36
3786, -54
"al6"
4596, 261
4716, 201
4776, 111
4791, 51
4791, -9
4791, -69
away 
Hrep (ordinary 
--Rep 
"al5" 
4086, 291
"al8"
"rep4"
)3945, 186
where 
4011, 276
3891, 216
3786, 156
3681, 96
3606, 51
3591, -54
3591, -84
3795, 231
3705, 336
3600, 456
3435, 576
3315, 666
3225, 801
3150, 936
3075, 1056
3030, 1116
3000, 1161
3681, 1395
3831, 1275
3936, 1065
3981, 885
3996, 660
3996, 420
4011, 210
4011, 75
4011, -75
--Rep1b 
reform 
)3390, 315
3561, 426
3891, 651
fields 
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textgo
cap-camp
text1
camp1
camp1
camp2
camp2
camp1
camp2
cap-camp
cap-camp
text1a
RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
text1b
RNApol
RNApol
text2
Group
text3
text4
leftrans
leftrans
rightrans
rightrans
text5
RNApol
WUngroup
text6
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
rna-s
leftrans
leftrans
rightrans
rightrans
trans
text7
rna-s
leftrans
leftrans
rightrans
rightrans
trans
trans
rna-s
Group
RNApol
RNApol
sendToBack
RNApol
text8
text9
WUngroup
WUngroup
rep1b
Group
WUngroup
rep1b
rep1b
Group
text1
text1a
text1b
text2
text3
text4
text5
text6
text7
text8
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textgo
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trans
horizPos:by
horizPos:to
horizPos
"textgo"
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textgo
RNApol
rna-s
text0.5
"text0.5"
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text0.5
No lactose is present so the lac repressor binds to the operator...he probability that the RNA polymerase will bind to the promoter. The repressor also increases this probability.he RNA polymerase for the promoter
text1
"text1"
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text1
Cyclic AMP binds to the CAP to form the CAP-cAMP complex. This then binds to the CAP siteeeeore readily.
text1.5
"text1.5"
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text1.5
The RNA polymerase binds to the DNA and moves along the DNA strand until it reaches the promoter..reg##
text2
"text2"
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text2
The CAP-cAMP complex interacts with the RNA polymerase increasing the probability that the RNA polymerase will bind to the promoter. The repressor also increases this probability...he RNA polymerase for the promoter
text3
"text3"
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text3
The repressor stops the RNA polymerase from carrying out transcription so no mRNA is synthesised. This condition is observed until lactose is present in the cell. ell.   
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REPEAT OR MOVE ON TO THE NEXT PAGE
Press the "Animate" button
c) Events when Lactose & Glucose are absentttt.   concentration low
Cyclic AMP
RNA polymerase
Repressor
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Animation 4
Animate
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"camp1"
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"cap"
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Basic
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4count
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"textgo"
"text1"
--Repressor protein (
rep) moves 
screen 
)4668, -384 
4608, -324
4533, -279
4428, -189
4278, -54
4143, 96
4008, 201
3783, 351
3573, 471
3363, 606
3183, 696
3003, 816
2718, 996
2298, 1191
"text2"
--RNA polymerase 
squashes up against 
repressor 3 times
"RNApol" 
)-1095, 510
-1080, 420
-1005, 435
-945, 435
-900, 480
-825, 510
-765, 525
-675, 630
-585, 705
-465, 780
-315, 855
-150, 1020
0, 1230
240, 1485
615, 1485
1065, 1485
1125, 1470, 2298, 2185
1185, 1470, 2298, 2185
1260, 1470, 2298, 2185
1335, 1470, 2298, 2185
1395, 1470, 2298, 2185
1425, 1470, 2298, 2185
1395, 1470, 2298, 2185
1365, 1470, 2298, 2185
1305, 1470, 2298, 2185
1215, 1470, 2298, 2185
1155, 1470, 2298, 2185
1125, 1470, 2298, 2185
1185, 1470, 2298, 2185
1260, 1470, 2298, 2185
1335, 1470, 2298, 2185
1395, 1470, 2298, 2185
1425, 1470, 2298, 2185
1395, 1470, 2298, 2185
1365, 1470, 2298, 2185
1305, 1485, 2298, 2185
1215, 1500, 2298, 2185
1155, 1515, 2298, 2185
1125, 1470, 2298, 2185
1185, 1470, 2298, 2185
1260, 1470, 2298, 2185
1335, 1470, 2298, 2185
1395, 1470, 2298, 2185
1425, 1470, 2298, 2185
1395, 1470, 2298, 2185
1335, 1470, 2298, 2185
1260, 1500, 2298, 2185
1185, 1515, 2298, 2185
1125, 1515, 2298, 2185
"rep"
default 
buttonUp
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textgo
text1
text2
RNApol
RNApol
text1
text2
RNApol
textgo
default
Basic
The lac operon has an inefficient promoter, meaning that the RNA polymerase  has a low probability of binding to the promoter. This means that the normal rate of transcription of the  lac operon is low. 
The 'Catabolite Activator Protein' (CAP), when bound to cyclic AMP, causes an increase in the rate of transcription by two possible methods:
1. CAP  may induce a bend in the DNA of approximately 90
 which is usually induced by the RNA polymerase. DNA bending may encourage RNA polymerase - promoter association, or produce elastic energy which may be used later on in transcription.   
 2. CAP may increase the rate of formation of the closed complex by directly interacting with the RNA polymerase, decreasing the probability of dissociation of the RNA polymerase from the promoter. However this seems less likely from evidence gained from the study of other operons where the promoter and CAP site are further apart.     nsidered.    
"The CAP 
a dimer 
two 22,500 dalton polypeptide chains. 
5can only bind 
Fsite 
complexed 
fcyclic AMP, due 
a change 
shape 
;protein. Binding 
-cAMP 
[results 
a increased rate 
transcription."
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The CAP is a dimer of two 22,500 dalton polypeptide chains. The CAP can only bind to the CAP site when it is complexed with cyclic AMP, due to a change in shape of the protein. Binding of the CAP-cAMP complex to the CAP site results in a increased rate of transcription.
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BIBLIOGRAPHY
D. Voet &  J.G Voet- BIOCHEMISTRY-  published  1990   Pages 868-870
L. Styrer - BIOCHEMISTRY - 3rd Edition, published 1988, Pages 799 - 805
B. Lewin - GENES IV - published 1990, Pages 240 - 261 
W.A. Rees et al. - Evidence of DNA Bending in Transcription Complexes                                                           Imaged by Scanning Force Microscopy -SCIENCE, Vol 260, 11th June 1993333333333333333 11th June 1993
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Summary of events under different conditions
a) Lactose absent, glucose absent:
Repressor binds to operator. 
Glucose low, cAMP high 
 CAP-cAMP complex binds to CAP site.
RNA polymerase binds readily but no transcription due to presence of repressor
b) Lactose absent, glucose present:
Repressor binds to operator.
Glucose high, cAMP low 
 CAP cannot bind to CAP site
RNA polymerase binds but no transcription due to presence of repressor.
								Continued overleaf.
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ZhorizPos
"textgo"
"text0.5"
--Repressor protein (rep) moves 
)4953, -429
nthe 
4923, -279
4863, -69
4803, 21
4698, 141
4548, 261
4383, 351
4203, 471
4023, 576
3858, 711
3678, 831
3438, 951
3258, 1056
3003, 1131
"text1"
--CAP 
screen
"cap" 
)-585, 2715
-540, 2685
-465, 2640
-375, 2565
-255, 2505
-150, 2445
-45, 2370
90, 2265
150, 2220
225, 2160
255, 2145
--2 molecules 
cAMP (camp1, camp2) 
binding sites 
, are hidden 
be replaced 
Ycomplex 
g) which 
)-75, 3159
15, 3084
135, 2949
195, 2904
225, 2874
285, 2829
345, 2769
390, 2709
420, 2664
420, 2589
)-75, 3459
-15, 3429
45, 3369
105, 3309
180, 3249
240, 3144
285, 3099
345, 3009
405, 2979
450, 2919
510, 2889
555, 2844
600, 2814
630, 2754
645, 2709
645, 2679
660, 2649
660, 2589
)249, 2157
354, 2127
519, 2112
654, 2097
789, 2067
909, 2052
999, 2037
1089, 2007
1179, 1977
1254, 1962
1344, 1947
1389, 1902
1434, 1902
1464, 1857
1509, 1797
--RNA polymerase 
forth along 
steps 
375, keeping
--verticle 
constant.
"RNApol" 
)8430, 165
8295, 255
8130, 345
7890, 495
7785, 540
7665, 585
7500, 645
7380, 690
7170, 795
7005, 915
6840, 1035
6630, 1230
6510, 1320
6450, 1350
6360, 1440
6360 
3735 
H-375
, 1440
3735 
6735 
, 1440
enters 
DNA, jumps over CAP!
suggestions 
problem would be appreciated)
promoter 
6735, 1365
6855, 1320
7035, 1305
7095, 1245
7245, 1155
7365, 1125
7470, 1095
7545, 975
7740, 855
7845, 840
7995, 810
8055, 795
8160, 780
8370, 765
"text2"
)-1095, 1410
-975, 1410
-765, 1410
-555, 1410
-375, 1410
-240, 1410
-120, 1410
-15, 1410
105, 1410
240, 1410
315, 1305
465, 1155
570, 1095
615, 1005
660, 885
885, 780
990, 720
1110, 720
1260, 765
1365, 780
1545, 870
1695, 900
1860, 975
2175, 1095
2265, 1305
2265, 1455
"text3"
--CAP-
fields 
"rep"
default
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text1
camp1
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RNApol
RNApol
RNApol
RNApol
RNApol
RNApol
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RNApol
RNApol
text3
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RNApol
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"quest3" 
"quest4" 
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3.  The repressor binds to:sor:
Promoter
Operator
Lactose
Allolactose
CAP siteee
4. Lactose binds to :::::::::::::::::::
quest3
Repressor
Operator
Catabolite Activator Protein
Permease
B-galactosidase
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B"k" 
B"l" 
B"m" 
B"n" 
B"o" 
B"p" 
B"q" 
B"r" 
B"s" 
B"t" 
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"quest5" 
"quest6" 
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5. Allolactose binds to ::::or:
Promoter
Operator
Repressor
CAP site
Lactose permease
6. The Catabolite Activator Protein binds to ::
Allolactose
CAP site
Cyclic AMP
Promoter
Operator
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B"u" 
B"v" 
B"w" 
B"x" 
B"y" 
B"z" 
B"a1" 
B"b1" 
B"c1" 
B"d1" 
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"quest7" 
"quest8" 
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7. High glucose concentration leads to :
Low rate of transcription
High concentration of cyclic AMP
Repressor dissociates from operator
RNA polymerase cannot bind to promoter
Reduced entry of lactose into cell
8. If cellular glucose concentration falls :
Lactose concentration rises
Cyclic AMP concentration falls
Allolactose concentration changes
Cyclic AMP concentration rises
Lactose concentration falls 
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B"e1" 
B"f1" 
B"g1" 
B"h1" 
B"i1" 
B"j1" 
B"k1" 
B"l1" 
B"m1" 
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9. The repressor :::::::::::::::7
Increases affinity of RNA polymerase for promoter
Decreases affinity of RNA polymerase for promoter
Blocks transcription
Increases rate of transcription
Binds when glucose is present as a substrate
10. The binding of the CAP-cAMP complex to the CAP site ::
Decreases the probability of RNA polymerase binding to the promoter
Stops the repressor from binding to the operator
Decreases the rate of transcription by causing a bend in the DNA
Increases the rate of transcription by interacting with RNA polymerase
Occurs when the glucose level is low
s are low
d as substrate
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B"w1" 
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+x.40
Answers to Lac Operon Questions
The answers to the problems that you got wrong can be seen below. Once you have read the correct answer click the mouse in the white box to move onto the next answer.
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answer20
"answer20"
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answer20
 Question 20:
The DNA sequences that exhibit  two-fold axes of symmetry are the operator and the CAP site. These symmetrical sites are involved in the binding of the repressor and CAP-cAMP complex to the repressor site and CAP site respectively.to the DNA.
answer19
"answer19"
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answer19
 Question 19:
The maximum number of molecules of cyclic AMP the Catabolite Activator Protein can bind is 2 - one in each subunit of the CAP. inding of the appropriate molecule to the DNA strand.
answer18
"answer18"
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answer18
 Question 18:
 The maximum number of allolactose molecules that the repressor can bind is four. However, only two must bind before the repressor can dissociate from the operator. the DNA strand.
answer17
"answer17"
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answer17
 Question 17:
 The catabolite activator protein is a dimer consisting of two 210 residue subunits. Each subunit is able to bind one molecule of cyclic AMP.iate from the operator. the DNA strand.
answer16
"answer16"
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answer16
 Question 16:
 The function of b-galactosidase is hydrolyse the glycosidic bond of the lactose to produce glucose and galactose. Both these molecules can be used for energy and as a carbon source.
answer15
"answer15"
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answer15
 Question 15:
 The repressor molecule is a tetramer although the repressor binds to the operator using only two of the possible four binding sites.es can be used for energy and as a carbon source.
answer14
"answer14"
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buttonUp
answer14
answer14
"answer14"
"answer14a"
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answer14
answer14a
 Question 14:
 The dissociation constant of the repressor-operator complex is 10  M, meaning that the binding is practically irreversible without the inducer.    for energy and as a carbon source.
answer14a
-13 M
answer13
"answer13"
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buttonUp
answer13
 Question 13:
 Allolactose is the inducer because its presence brings about the process of transcription and the production of the proteins. None of the others can directly induce transcription.
answer12
"answer12"
buttonUp
buttonUp
answer12
 Question 12:
  Lactose has the configuration Galactose b(1
4) Glucose ut the process of transcription and the production of the proteins. None of the others can directly induce transcription.
answer11
"answer11"
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answer11
 Question 11:
 The CAP site binds only the catabolite activator protein-cyclic AMP complex. It will not bind the CAP on its own.he proteins. None of the others can directly induce transcription.
answer10
"answer10"
buttonUp
buttonUp
answer10
 Question 10:
 Low glucose concentration results in a high level of cyclic AMP. Under these conditions the CAP-cAMP complex is formed. The binding of this complex to the CAP site increases transcription by interacting with the RNA polymerase or by forming a bend in the DNA.nteracting with the RNA polymerase or by forming a bend in the DNA.by forming a bend in the DNA.
answer9
"answer9"
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answer9
 Question 9:
 The repressor blocks transcription by stopping the RNA polymerase from moving off the promoter. The repressor also increases the affinity of RNA polymerase for the promoter by 100 fold. The result of this is that when lactose enters the cell the RNA polymerase is ready to start transcription immediately, leading to very quick production of the proteins.   
answer8
"answer8"
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answer8
 Question 8:
 If the cellular glucose concentration falls the cyclic AMP concentration rises. Glucose concentration has no effect on the lactose concentration or the allolactose concentration.   on or the allolactose concentration.   enters the cell the RNA polymerase is ready to start transcription immediately, leading to very quick production of the proteins.   
answer7
"answer7"
buttonUp
buttonUp
answer7
 Question 7:
 A high glucose concentration leads to a low rate of transcription. In the absence of cyclic AMP the CAP cannot bind to the CAP site so the promoter remains relatively inefficient. Thus only small amounts of permease made leading to low lactose uptake into the cell. is made so only a small amount of lactose enters the cell.  uction of the proteins.   
answer6
"answer6"
buttonUp
buttonUp
answer6
 Question 6:
 The catabolite activator protein can only bind to cyclic AMP. It is the complex between the two that can bind to the CAP site.   ecient. It also leads to the reduced entry of lactose because only a small amount of permease is made so only a small amount of lactose enters the cell.  ion immediately, leading to very quick production of the proteins.   
answer5
"answer5"
buttonUp
buttonUp
answer5
 Question 5:
 Allolactose binds to the repressor. This causes a conformational change in the repressor so that the repressor can no longer bind to the operator.  ds to the reduced entry of lactose because only a small amount of permease is made so only a small amount of lactose enters the cell.  ion immediately, leading to very quick production of the proteins.   
answer4
"answer4"
buttonUp
buttonUp
answer4
 Question 4:
 Lactose binds to permease and b-galactosidase. The permease transports the lactose into the cell and the b-galactosidase hydrolyses the lactose into glucose and galactose.  f lactose because only a small amount of permease is made so only a small amount of lactose enters the cell.  ion immediately, leading to very quick production of the proteins.   
answer3
"answer3"
buttonUp
buttonUp
answer3
 Question 3:
 The repressor binds to the operator to stop transcription. It also binds allolactose which causes a conformational change and lifts repression.      .   and galactose.  ry of lactose because only a small amount of permease is made so only a small amount of lactose enters the cell.  ion immediately, leading to very quick production of the proteins.   
answer2
"answer2"
buttonUp
buttonUp
answer2
 Question 2:
 RNA polymerase binds to the promoter in order to initiate transcription. It also binds to the CAP-cAMP complex, increasing the efficiency with which the enzyme can bind to the promoter.       nly a small amount of permease is made so only a small amount of lactose enters the cell.  ion immediately, leading to very quick production of the proteins.   
answer1
"answer1"
buttonUp
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answer1
 Question 1:
The three genes that the Lac Operon controls are b-galactosidase, lactose permease and lactose transacetylase - i.e those that control the entry and metabolism of lactose.
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THE END
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">$H(
KbLJNzN
RNApol
rna-s
!"ab3"
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!"ab2"
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!"ab1"
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Animate2
Animate
Press the "Animate" button
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!"pa"
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^0d1u
text1
"text1"
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text1
Repressor increases affinity of RNA polymerase for promoter so the enzyme binds to the DNA more readily.
text2
"text2"
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text2
Allolactose binds to the repressor causing a conformational change which results in the repressor leaving the operator.
text3
"text3"
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RNA polymerase free to carry out transcription.nformational change which results in the repressor leaving the operator.
^0r5u
text4
"text4"
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RNA polymerase binds, then melts a section of DNA into single strands to form  the open complex.
text5
"text5"
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Abortive initiation occurs until the sigma unit dissociates and the core enzyme can move along the DNA.
^028u
text6
"text6"
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text6
Elongation e binds to DNA, melts a section into single strands to form open complex.
^0r9u
text7
"text7"
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text7
Termination
binds to DNA, melts a section into single strands to form open complex.
text8
"text8"
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f;>;c;
Strand of mRNA formed
text9
"text9"
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When the lactose concentration decreases the allolactose dissociates from the repressor so the repressor can once more bind to the operator....
~=V={=
Allolactose
L>$>I>
Repressor
RNA polymerase
`?8?]?
Allolactose binding site
"al1"
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"al2"
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"al3"
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"al4"
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LI$III
Events when lactose is present:
trans
	3	lJ
intrans
"trans"
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trans
rightrans
	3	`K
leftrans
outrans
RL*LOL
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rep1b
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!rL`L`L
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+f,*-
4n526
8t96:
AHB^?
bacteriaah
:PHYSSIZE
Teaching and Learning Technology Programme
produced by the
 The Lac Operon      emmunoglobulins
bacteriaah2
 Andrew MacLennan & John M Basford
Biochemistry Department
University of Wales, Cardifffffffffffffffff
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Start
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You can distribute the unmodified material freely and modify it to your own requirements. However, we ask the following:
1. By all means give yourself credit for your work in your books but please leave this page unaltered in this book.
2. It is important that teaching material of this kind is disseminated as widely as possible, so please ensure that your material is also freely available.
3. Please send a copy of any modified or expanded versions of this program to Dr J.M Basford, Department of Biochemistry, University of Wales, Cardiff, CF1 1ST , Tel 44 222-874119 Fax 44 222-874116. 
Internet Basford @Cardiff.ac.uk
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Basic
UDUgmJ
System
Wingdings
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The Lac Operon
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Wingdings
Times New Roman
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Arial
-- Puts the 
mode 
hides 
menus 
file 
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Basic
Questions
FirstPage
1st Page
This section contains 20 questions based on the information in the previous pages which will take about 10 minutes to complete. Once in the quiz it is only possible to go forwards - it is not possible to exit or return to previous pages. 
N.B. For each question there are 5 checkboxes. The correct answer    
         may  involve the checking of any number of boxes from 0 to 5.
GOOD LUCK!
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Basic
		      INTRODUCTION
The lac operon is found in the bacterium E.coli. The proteins coded for by this gene cluster are required for the uptake and utilisation of lactose. The genes are only switched on when the proteins are required, i.e. only when lactose is present.  This follows the rule of survival in bacteria that proteins are made when they are needed.
Lactose is a disaccharide with the structure [ b-galactose (1
4) b-glucose ]. Lactose may be utilised both as an energy source and as a carbon source. In order to be utilised it must be taken up by the cell, hydrolysed to glucose and galactose and then enter the glycolysis sequence.
operon
--Script that opens a simple dialog box
" An operon 
a gene cluster where several genes are under the control 
a single promoter."
buttonDown
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 An operon is a gene cluster where several genes are under the control of a single promoter.
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Lactose
Lactose
b - Galactosidase
Glucose + Galactose
TCA cycle
Glycolysis
Permease
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!4#X#
Structure of the Lac Operon
Move the mouse into each of the coloured boxes.
Dialog
"Dialog"
mouseEnter
mouseEnter
Dialog
siteeeeee
--Promoter--
Operator
Lac Z
Lac Y
Lac A
-- Text 
removed 
cursor leaves the coloured areas
"dialog"
mouseleave
mouseleave
dialog
CAP site
Put "CAP site - binds Catabolite Activator Protein 
attached 
cyclic AMP, i.e. only 
the glucose concentration 
low. The 
qattachment enhances 
7efficiency 
fwhich 
LRNA polymerase 
apromoter, 
hence 
urate 
transcription. Like 
operator 
has a two-fold axis 
symmetry 
binding 
CAP-cAMP complex." 
"Dialog"
mouseEnter
mouseEnter
CAP site - binds Catabolite Activator Protein when attached to cyclic AMP, i.e. only when the glucose concentration is low. The CAP attachment enhances the efficiency with which the RNA polymerase binds with the promoter, and hence the rate of transcription. Like the operator it has a two-fold axis of symmetry for the binding of the CAP-cAMP complex.
Dialog
Promotor
MouseEnter
"Promoter region - site 
which RNA polymerase binds 
order 
initiate transcription. It occupies approximately 70 bp, starting 
-50 upstream 
finishing 
+20 downstream 
"Dialog"
MouseEnter
MouseEnter
Promoter region - site to which RNA polymerase binds in order to initiate transcription. It occupies approximately 70 bp, starting at position -50 upstream of the transcription start site and finishing at position +20 downstream of the transcription start site.
Dialog
Operator
"Operator 
repressor binding site - 
stopping transcription 
being initiated. It 
approximately 26 bp 
\, starting 
-5 upstream 
ending 
+21 downstream 
. The operator has a two-fold axis 
symmetry which plays a part 
"Dialog"
mouseEnter
mouseEnter
Operator or repressor binding site - repressor binds to this site stopping transcription from being initiated. It is approximately 26 bp long, starting at position -5 upstream from the transcription start site and ending at position +21 downstream from transcription start site. The operator has a two-fold axis of symmetry which plays a part in the binding of the repressor.
Dialog
Lac Z
Put "LacZ: gene that codes 
Beta-galactosidase - breaks the glycosidic bond 
lactose 
yield glucose 
galactose. 
a tetramer 
four 125,000 dalton polypeptide chains." 
"Dialog"
mouseEnter
mouseEnter
LacZ: gene that codes for Beta-galactosidase - breaks the glycosidic bond in the lactose to yield glucose and galactose. Beta-galactosidase is a tetramer of four 125,000 dalton polypeptide chains.
Dialog
Lac Y
Put "LacY: gene that codes 
lactose permease - a membrane bound protein 
6allows the transport 
Athrough 
cell. The 
8has a molecular weight 
30,000 daltons." 
Sext 
"Dialog"
mouseEnter
mouseEnter
LacY: gene that codes for lactose permease - a membrane bound protein that allows the transport of lactose through the membrane into the cell. The protein has a molecular weight of 30,000 daltons.
Dialog
Lac A
"LacA: gene that codes 
lactose transacetylase - transfers 
-CoA 
.. The reason 
xfully understood but may give 
advantage 
bacteria are grown 
a medium containing analogs 
7cannot metabolise, because acetylation results 
detoxification 
excretion." 
"Dialog"
mouseEnter
mouseEnter
LacA: gene that codes for lactose transacetylase - transfers acetyl group from acetyl-CoA to lactose. The reason for this is not fully understood but may give an advantage when bacteria are grown in a medium containing analogs of lactose that the bacteria cannot metabolise, because acetylation results in detoxification and excretion.
Dialog
Overlap
"There 
overlap between the promoter region 
operator. However, 
(RNA polymerase 
;repressor can bind 
Qoperon 
\same 
I- they are 
xmutually exclusive." 
"Dialog"
mouseEnter
mouseEnter
There is an overlap between the promoter region and the operator. However, the RNA polymerase and the repressor can bind to the operon at the same time - they are not mutually exclusive.
Dialog
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		Transcription of the Lac Operon
Process of Transcription:
	a) The operator is free of repressor.
	b) RNA polymerase binds to the promoter to form a closed complex.
	    
  	A short sequence of  the DNA enclosed by the enzyme 'melts' into single strands 			to form the open complex.
  	Transcription  starts  but  if  the  sigma  subunit does  not   then dissociate  the 			transcription process aborts releasing a small piece of RNA. This is known as 			abortive initiation and is repeated until the sigma subunit dissociates.
	c) Elongation - RNA polymerase moves along the DNA strand synthesising RNA 		until terminator reached.
	d) Termination.
4 of  30
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RNApol
rna-s
textall
text0.5
"text0.5"
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text0.5
RNA polymerase binds to the DNA then moves up and down the DNA strand until the promoter is reached. The interaction between the promoter and RNA polymerase is weak so the enzyme has a low probability of binding to the promoter........................................
text1
"text1"
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When RNA polymerase does bind to the DNA, it melts a section into single strands to form open complex. Abortive initiation occurs until sigma unit dissociates and the core enzyme can move along the DNA.
text2
"text2"
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text2
Abortive initiation occurs until sigma unit dissociates and the core enzyme can move along the DNA.
text3
"text3"
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text3
Elongation e binds to DNA, melts a section into single strands to form open complex.
text4
"text4"
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text4
Termination
binds to DNA, melts a section into single strands to form open complex.
text5
"text5"
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text5
Strand of mRNA formed
!"ab3"
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!"ab2"
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!"ab1"
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Animate2
Animate
Press the "Animate" button
Repressor
RNA polymerase
Allolactose binding site
buttonUp
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trans
intrans
"trans"
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trans
rightrans
leftrans
outrans
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!"pa"
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5 of  30
Events in Transcription:
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Transcription of Lac Operon under different physiological conditions.
a) Events when lactose is absent::
A small amount of lac repressor protein is continually made by the cell.
The repressor binds to the operator with a dissociation constant of 10     M, so  binding is virtually irreversible. The binding of the repressor increases the affinity of the RNA polymerase for the promoter 100 fold. This occurs so that when lactose does become available the initiation of transcription is very rapid because the enzyme is already bound.
The RNA polymerase cannot initiate transcription due to the presence of the repressor so none of the proteins are synthesised..
repressor protein
-- Script that opens a simple dialog box 
"The lac repressor protein 
a tetramer 
four 38,000 dalton polypeptide chains. Each 
the subunits has two recognition sites - one 
,operator 
9other 
Cinducer molecule allolactose. However, only 
`molecules 
% need 
bind 
repression 
transcription 
be lifted."
buttonDown
buttonDown
The lac repressor protein is a tetramer of four 38,000 dalton polypeptide chains. Each of the subunits has two recognition sites - one for the operator and the other for the inducer molecule allolactose. However, only two molecules of allolactose need to bind to the repressor for repression of transcription to be lifted.
6 of  30
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RNApol
rna-s
Events when  lactose is absent::o
Animate
Animate
text1
"text1"
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text1
No lactose is present so repressor binds to the operator.
text2
"text2"
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text2
The repressor increases the affinity of the RNA polymerase for the promoter. The RNA polymerase binds more readily to the promoter. However, no transcription can take place as the repressor blocks the RNA polymerase.      
textgo
"textgo"
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Repressor
RNA polymerase
Allolactose binding site
7 of  30
Press the "Animate" button
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b) Lactose present as substrate::::::
Lactose
Permease
Lactose
[Allolactose] 
There is a small amount of permease always present in the cell membrane of the E.coli so lactose is able to enter the cell, but the rate of uptake is slow.
Some of the lactose is converted to allolactose which binds to the repressor, causing the affinity of the repressor for the operator to be lost             
Some of the lactose is converted to allolactose which binds to the repressor, reducing the affinity of the repressor for the operator.                slow.
Some of the lactose is converted to allolactose which binds to the repressor, causing the affinity of the repressor for the operator to be lost.            
allolactose
that opens a simple dialog box
"Allolactose 
isomer 
whose structure 
[Beta Gal (1-6) 
luc].It 
known 
inducer molecule because 
brings about the initiation 
transcription"
buttonDown
buttonDown
Allolactose is an isomer of lactose whose structure is [Beta Gal (1-6) Beta Gluc].It is known as an inducer molecule because it brings about the initiation of transcription
The repressor dissociates from the operator allowing transcription to proceed. The three proteins are synthesised in large quantites.The elevated permease level allows  lactose to  enter the cell at a much higher rate than before.  e. rate than before. 
8 of  30
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barchart
-- y1 
the height 
bar (glucose), y2 
cAMP)
-- speed 
how much 
Gbars increase 
decrease 
-- On entering 
8are returned 
their 
positions
4y1, y2
"barchart" 
2670, 3210, 3360, 4080
3735, 3210, 4425, 4080
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barchart
barchart
speed
Glucose
Cyclic AMP
	^	`	p
Cyclic AMP (cAMP) is a secondary messenger molecule in many cells. The level of cyclic AMP is controlled by the amount of glucose present in a cell. When the glucose concentration is high, the cyclic AMP concentration is low. As the glucose concentration decreases the cyclic AMP concentration increases. Cyclic AMP is therefore known as the 'starvation signal'.
	% 1_
"Adenosine-3',5'-cyclic monophosphate (cAMP) 
formed 
Hthe action 
adenylate cyclase. The 5' 
)3' hydroxy 
9ribose are linked together 
d a ring."
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Adenosine-3',5'-cyclic monophosphate (cAMP) is formed from AMP by the action of adenylate cyclase. The 5' phosphate group and the 3' hydroxy group of the ribose are linked together to form a ring.
Glucose 
Concentration 
(mM)%)
--See 
--y1 
)their maximum height 
2 = 2280
--If 
2 has a value > 2280 
C bar 
bellow 
Ncan be increased.)
--When 
Bpressed 
?(y2/cAMP) decreased 
H180 
--minimum 
(4080) 
which 
will 
no further, 
(y1/glucose) increases 
reached 
-- remains 2280
4y1, y2, speed
y1 > 2280
y1 < 2280
y2 < 4080
y2> 4080
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Increase
[Glucose]   
-- See 
increase glucose 
--When 
Bpressed height 
bar (y1/
,) decreased 
H180 
--minimum value (4080) 
which 
will 
no further, 
[2/cAMP) increases 
Zmaximum 
reached 
remains
--2280
4y1, y2, speed
y1 < 4080
y1 > 4080
y2 > 2280
y2 < 2280
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Decrease
[Glucose]   
height
Cyclic AMP 
Concentration 
(x 10   M)
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b -Galactosidasee
Lactose
Lactose
Glucose + Galactose
TCA cycle
Glycolysis
Permease
Glucose
The situation is more complex than this because glucose is the preferred substrate of the E.coli. Therefore, if glucose is present then the bacterium will metabolise the glucose in preference to the lactose- no additional enzymes are needed.  eded.  etabolized.tabolized. be metabolized.metabolized.abolized.tabolized.tabolized.e metabolized.
However -
10 of  30
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