Download Unit 4: Genetic Engineering and Gene Expression

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Unit 4: Genetic Engineering and Gene Expression Study Guide
General Questions about the GEs
1. What is the purpose of genetic engineering/synthetic biology?
To change the genetic makeup of cells so that they express new traits
2. What is the very important relationship between DNA and proteins?
DNA holds the information that codes for proteins, the workers of the cell.
3. Does a cell always express a gene, even if it does not need the protein?
No, the cell will only express a gene which codes for a needed protein
4. How does a cell know when to turn on/off genes?
Specific environmental signals turn on/off genes.
pGLO Lab
5. What type of molecule are restriction enzymes and what do they do?
Like all enzymes, they are proteins.
Their function is to cut DNA into fragments.
6. Why are “sticky ends” cut by certain restriction enzymes important?
Sticky ends are single stranded ends of the double stranded DNA that can
bond to another single stranded end that is complementary to it.
7. Why do you need to use the same restriction enzyme for both the
plasmid and the target gene?
The same restriction enzyme needs to be used in order to have the same
complementary bases on the sticky ends.
8. What is a plasmid?
A circular piece of bacterial DNA that scientists use to carry genes into cells.
9.
How do we use restriction enzymes to make a “recombinant” plasmid?
We cut the target gene out of the DNA it comes from and the plasmid with the SAME restriction enzyme.
The sticky ends of each are complimentary, so they bond and form a recombinant plasmid.
10. Since DNA cannot read itself, we had to force the plasmid into bacteria. How did we do this? What lab
procedure transforms bacteria with new DNA?
“HEAT SHOCK” allowed us to force the recombinant plasmids
into the bacteria, thus transforming the bacteria.
11. When the gene was turned on, what molecule was actually glowing in the bacterial cells?
The Green Florescent PROTEIN – GFP (remember, proteins do the work of the cell!)
12. Why did the bacteria plated without sugar NOT glow, even though the bacteria plated on each had the GFP
gene? (What is the role of sugar?)
Even though the bacteria had the GFP gene, it was not yet expressed. The gene
is only
read when the inducer molecule is present. The sugar acts as the
inducer molecule by removing the repressor protein from a regulatory segment,
causing RNA
Polymerase to start reading the gene.
No Sugar
Sugar
13. HOW does the sugar allow the glowing protein to be made?
(Underline the terms inducer, repressor & RNA polymerase in your answer)
Sugar is the inducer. When a gene is turned off, the repressor sits on a
regulatory segment of DNA, preventing RNA polymerase from reading/
transcribing the gene being controlled. When the inducer is
present in the environment, it attaches to the repressor,
causing it to change shape and detach from the DNA. Then,
RNA polymerase is able to finally read and express the gene
14. What does it mean to not “express” a trait even though one might possess the DNA in their genes? Why do we
say a gene is “turned on” or “turned off”?
Expressed = turned on = the gene is read/transcribed, so the protein is being produced
Not expressed = turned off = the gene is NOT being transcribed, so NO protein is being produced
15. While we do not mass-produce the glowing protein made by these bacteria, some medicines are indeed made in
the same way our glowing protein was made. What medicine did we talk about in class that is made this way,
and is used to keep diabetics healthy?
Insulin
16. What is the next step, what is the problem with giving a patient the sample of bacteria that have
produced the protein of interest? What must be done to the bacteria and proteins before given to patients?
Bacteria naturally make several different proteins that do the work of the bacteria. Therefore,
we need to separate the protein we forced the bacteria to make (like insulin) from all those
other proteins, because we do not want to inject patients with bacterial proteins.
17. What are some ways in which the GFP gene is being used in medical research? (Think back to the article, “Green
pig gives birth to glowing piglets”)
Spread of cancer cells, organ transplants
GMO Questions
18. How is recombinant DNA technology used in the agricultural industry?
How can we test to see if foods are genetically modified?
Genes are placed in the cells of agricultural products (fruits,veggies,etc) to
make them more pest resistance or have a higher output, increased nutrition or longer shelf-life.
19. What do we have to collect from the food?
We need to collect their DNA
20. What lab technique did we use to make more of the DNA, so that we could run the amplified DNA segments in a
gel? (Think back to lab techniques in Unit 2 – DNA)
Polymerase Chain Reaction, or PCR – we use a thermalcycler machine to perform PCR, which makes copies
(amplifies) a specific segment of DNA that we are targeting
21. What do we look for in the gel to determine whether or not it has been genetically modified?
We look so see if the specific GMO gene is present by looking for a band in the
gel that coincides with the size of that gene.
EPIGENETIC QUESTIONS
22. What is epigenetics?
the study of these chemical reactions and the factors that influence them
23. Define the word “histone” and how it relates to epigenetics.
The protein that DNA is wrapped around
24. Do Epigenetics change overtime? What can affect the epigenome?
Yes, Environmental factors such as diet, exercise, exposure to toxins, stress
25. What are the chemicals that can express or suppress certain genes?
Epigenetic tags
26. What is the difference between and active gene and an inactive gene?
 Inactive genes = tightly wrapped … makes genes unreadable/silenced
METHYL GROUPS ATTACHED
 Active genes = relaxed/unwound … makes genes accessible/readable
ACETYL GROUPS ATTACHED
27. How is research being done to test epigenetics? What type of people are researchers using?
In Madrid, twin studies to see how epigenetics change overtime.
28. As twins age, what happens to the number of epigenetic differences?
Their environments change. Signals from the environment act on the epigenome that active/silence different
genes.
(Diet, physical activity, exposure to toxins, stress)
29. Describe how epigenetics plays a role in the expression of the agouti
gene in mice.
All mammals have a gene called agouti. In mice, when the agouti gene
is…
unmethylated - it has a yellow coat, is obese, and prone to diabetes and
cancer.
methylated - (normal mice) it has a brown coat, and a low disease risk.
30. How does an epigenetic code differ from the DNA code?
Epigenetic code can change overtime, DNA code is fixed
31. During the “Lick Your Rats Activity”, what happens to a rat that receives a lot of nurturing in comparison to one
that receives little to no nurturing?
Rat pups who are highly nurtured by their mothers (licked, groomed, nursed) tend to grow up to be calm adults.
Rat pups who receive little nurturing tend to grow up to be anxious.