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MR. HAYES’ AP BIOLOGY CHAPTER GUIDEChapter 13 - Regulation of Gene Expression
1. Describe the typical components of an operon in an E. coli (prokaryotic) cell. (p. 238-239)
a. regulator gene - ____________________________________________________________
____________________________________________________________________________
b. promoter - ________________________________________________________________
____________________________________________________________________________
c. operator - _________________________________________________________________
____________________________________________________________________________
d. structural gene - ___________________________________________________________
____________________________________________________________________________
2. Jacob and Monod studied two types of E. coli operons, the ___ operon and the ___ operon. (p.239)
3. Think of the operon as a series of switches that are turned on and off depending on the immediate
needs of the bacterium. The trp operon exists like this in the “on” position. For E. coli, it periodically
needs the amino acid tryptophan to perform certain functions. When enough tryptophan is produced,
the amino acid shuts off the process by binding to an ________________ ceasing the producing of the
structural genes and, consequently, the ___________ needed to break it down. Sketch figure 13.1 and
summarize the trp operon in the presence and absence of tryptophan.
Tryptophan absent
Tryptophan present
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MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
a. summary of tryptophan absent - ________________________________________________
____________________________________________________________________________
____________________________________________________________________________
b. summary of tryptophan present - ________________________________________________
____________________________________________________________________________
____________________________________________________________________________
4. Describe the 3 genes that encode the enzymes needed to break down lactose in bacteria. (p. 239)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
5. Examine figure 13.2. Notice how the lac operon is continuously “off.” The ____________________
is perpetually bound to the operator which prevents the _____________ from binding to the promotor.
As a result, the _____________________ genes cannot be transcribed into mRNA and consequently
cannot express the enzymes to break down _______________ . However, when lactose is present,
it binds to the ______________________ which prevents the the ______________________ from
binding to the operator. That leaves RNA polymerase free to bind to the ______________ , facilitating
the transcription of lactose metabolizing genes and the enzymes needed to break down _________ .
lactose present
lactose absent
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MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
a. summary of lactose present - __________________________________________________
____________________________________________________________________________
____________________________________________________________________________
b. summary of present absent - __________________________________________________
____________________________________________________________________________
____________________________________________________________________________
6. Describe how lactose is considered an inducer of the lac operon. (p. 240)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
7. Fill in the matrix detailing the different mechanisms in eukaryotic cells that can modify genes (p. 241)
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Mechanism Description
transcriptional control
used in a way to keep genes turned off. Chromatin structure is one method of epigenetic inheritance which is the transmission of genetic information outside the coding sequences of a gene.
translational control
takes place in the cytoplasm occurs after protein synthesis. Only a functional protein is an active gene product.
posttranscriptional control
MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
8. Define the term chromatin. Where is it most evident? (p. 241)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
9. Differentiate between euchromatin and heterochromatin. (p. 242)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
10. What type of histone tail does heterochromatin contain? _________ . Euchromatin? ___________
11. When does euchromatin become genetically active? (p. 242)
__________________________________________________________________________________
12. Summarize figure 13.5 b and c. Be sure to describe how DNA becomes free for transcription and
the molecules involved.
b. __________________________________________________________________________
____________________________________________________________________________
c. __________________________________________________________________________
____________________________________________________________________________
13. Why do only females contain a barr body? How does a barr body prevent females from expressing
more genes than males? (p. 243)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
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MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
14. This goes against everything I’ve taught you about genetics, but there is way for females who are
heterozygous for an X-linked trait to express the recessive AND dominant allele in different cells!! This
is achieved by X-inactivation which produces a barr body. Take a look for yourself by summarizing
figure 13.6!
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
15. What does the term epigenetic inheritance generally refer to? Provide an example. (p. 243)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
16. What is the role of a transcription factor in a eukaryotic cell? (p. 244)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
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MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
17. Fill in the matrix regarding transcriptional control. (p. 244)
18. Transcription in eukaryotic cells requires
___________________ to bind to the promoter and the
___________________ to bind to the enhancer. The
enhancer may be far from the promoter, so the DNA
loops over itself so the transcription factor can bind to
the transcription activator via _____________________.
19. Where does post transcriptional control occur
and what does it include? (p. 244)
____________________________________________
____________________________________________
____________________________________________
20. What is the main benefit of alternative pre-mRNA splicing in humans? (p. 244)
__________________________________________________________________________________
__________________________________________________________________________________
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Component Description
transcription factor
transcription activator
enhancer
MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
21. What is implied about the proteins made from identical mRNA strands that have undergone
independent pre-mRNA splicing? (figure 13.8)
__________________________________________________________________________________
__________________________________________________________________________________
22. Scientists originally thought that 99% of DNA was
“junk” because it didn’t code for specific proteins.
Now we know that this DNA code for a specific
type of RNA called __________________________ .
23. Describe 3 ways in which sRNA can regulate gene
expression. (p. 245-246)
1.) ______________________________________
________________________________________
________________________________________
________________________________________
2.) _________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
3.) _________________________________________________________________________
___________________________________________________________________________
___________________________________________________________________________
24. Define a gene mutation. (p. 247)
__________________________________________________________________________________
__________________________________________________________________________________
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MR. HAYES’ AP BIOLOGY CHAPTER GUIDE
25. Fill in the matrix of the different causes of gene mutations. (p. 247-248)
26. How do proto-oncogenes and tumor suppressor genes (in conjunction with transcription factors)
contribute to the development of cancer? (p. 249)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
27. Summarize the two cell signaling pathways below. (figure. 13.13 and 13.14)
___________________________________ ___________________________________
___________________________________ ___________________________________
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Mutation Description Example
spontaneous
induced
point
frameshift