trp Operon Activity – Online Animations and Interactive
Learning
Website 1 –Sumanas Tutorial and Self-Quiz
http://www.sumanasinc.com/webcontent/animations/content/lacoperon.html
http://bcs.whfreeman.com/thelifewire/content/chp13/1302002.html
.
Website 2 – Lonestar Interactive
http://nhscience.lonestar.edu/biol/operon/ton.html
Operon Expressed (Turned-on)
1. Click “Operon On” to examine the parts of the lac operon (shown above). Then, click
“Animation” and watch the operon in action when it is turned-on.
2. Click “Next” at the bottom of the screen to move to the next situation where the operon
is turned-off.
Operon Not Expressed (Turned-off)
3. Click “Repressed - Operon Off” to examine the parts of the lac operon (shown above).
Then, click “Animation” and watch the operon in action when it is turned-on.
4. Click the “Quiz” button at the bottom of the page and take the self-quiz based on the
animations.
Website 3 – McGraw Hill Animation and Self-Quiz
http://highered.mcgrawhill.com/sites/007352543x/student_view0/chapter13/the_tryptophan_repressor.html
The Tryptophan Repressor
How do repressor proteins prevent the synthesis of mRNA? Repressor
proteins prevent the synthesis of mRNA by binding to DNA at a specific site
near the start of a gene or sequence of genes. The bound repressor protein
prevents molecules that are necessary for transcription from binding to
initiation sites. RNA polymerase cannot bind to the DNA and the synthesis of
RNA cannot occur. The configuration of the repressor protein must match
that of the binding site on the DNA. Often another molecule must bind to the
repressor to give it the proper configuration.
1
The trp operon consists of ________ genes that encode tryptophan biosynthesis
enzymes.
one
A)
two
B)
three
C)
four
D)
five
E)
2
In the absence of tryptophan, the trp repressor is
A)
B)
C)
D)
E)
3
B)
C)
D)
E)
inactive and cannot bind to the promoter.
inactive and can bind to the operator.
inactive and cannot bind to the operator.
operator.
promoter.
RNA polymerase.
trp genes.
trp repressor.
In the presence of tryptophan, transcription of the trp operon is on.
A)
B)
5
active and cannot bind to the operator.
In the presence of tryptophan, tryptophan binds to the
A)
4
active and can bind to the operator.
True
False
The trp repressor is a helix-turn-helix regulator protein.
A)
B)
True
False