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 - ________________________________________________________________

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c. operator - _________________________________________________________________

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d. structural gene - ___________________________________________________________

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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 - ________________________________________________

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b. summary of tryptophan present - ________________________________________________

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4. Describe the 3 genes that encode the enzymes needed to break down lactose in bacteria. (p. 239)

__________________________________________________________________________________

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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 - __________________________________________________

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6. Describe how lactose is considered an inducer of the lac operon. (p. 240)

__________________________________________________________________________________

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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)

__________________________________________________________________________________

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9. Differentiate between euchromatin and heterochromatin. (p. 242)

__________________________________________________________________________________

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10. What type of histone tail does heterochromatin contain? _________ . Euchromatin? ___________

11. When does euchromatin become genetically active? (p. 242)

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12. Summarize figure 13.5 b and c. Be sure to describe how DNA becomes free for transcription and

the molecules involved.

b. __________________________________________________________________________

____________________________________________________________________________

c. __________________________________________________________________________

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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!

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__________________________________________________________________________________

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15. What does the term epigenetic inheritance generally refer to? Provide an example. (p. 243)

__________________________________________________________________________________

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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.) _________________________________________________________________________

___________________________________________________________________________

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3.) _________________________________________________________________________

___________________________________________________________________________

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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)

__________________________________________________________________________________

__________________________________________________________________________________

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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