Download recombinant dna lab

Name: ______________________________________________ Date: _____________ Hour: ______
BIOLOGY B Genetic Recombination Lab.2016
DNA fragments from donor cells must become part of the genetic material of living cells before
the genes they contain can be activated. For example, DNA fragments may be combined with bacterial
DNA so that they can later be inserted into a bacterial cell. Bacteria often contain small circular DNA
molecules known as plasmids in addition to their chromosome.
Scientists use restriction enzymes to cut segments of genetic material from plasmids. When the
plasmids are cut, unpaired bases are left at the ends. These exposed bases are sometimes called ‘sticky
ends’ because new segments of DNA can be attached to them by hydrogen bonding as if they were
sticky, like tape. In this activity, you will make and use a model of the technique used to combine pieces
of DNA. In so doing you will form a new plasmid that contains a piece of foreign DNA. This new plasmid
is called recombinant DNA.
If a scientist would like to make many copies (clone) a human gene, he can use this technique.
First, he must identify the human gene in which he is interested. This gene is called the ‘gene of
interest’! He must then treat his sample of human DNA with the same restriction enzyme used to cut
the plasmid. By using the same restriction enzyme, the scientist makes certain that his human gene has
the same ‘sticky ends’ as the plasmid.
A new segment of DNA can be attached to the plasmid only if its exposed bases are
complementary to the exposed bases on the DNA of the plasmid. Once the complementary bases are
hydrogen bonded to each other, another enzyme, DNA ligase, adds the covalent bonds holding the
sugar-phosphate backbone of the DNA together. Once the plasmid is complete, it can be inserted into a
bacterium, and induced to transcribe and translate this new gene, making a human protein in a
bacterium!
Materials:
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Scissors
Pen or pencil of a contrasting color to write on the plasmids
Paper plasmids
Paper ‘human DNA’
Paper Restriction enzymes
Masking tape
Procedure:
1. Using your scissors, carefully cut out all 6 columns of the plasmid DNA. Then, tape the six
strips together in order. Strip #2 should be attached to the bottom of strip #1, strip #3
should be attached to the bottom of strip #2, and so on. When you are finished with this
part, you should have a ring of plasmid DNA.
2. Cut out the restriction enzyme BAM HI.
3. Cut out the segment of human DNA containing a ‘gene of interest’.
4. Now, carefully move the restriction enzyme along the human DNA, and find the two sites at
which BAM HI will cut the human DNA. The base sequence that BAM HI will cut is printed
on the restriction enzyme. When you find these two sites, mark them with a pencil the
same way they are marked on the restriction enzyme. Then, cut the human DNA along the
lines you drew.
5. Next, move the restriction enzyme along the plasmid, looking for the one site at which BAM
HI will cut the plasmid DNA. As you did with the human DNA, draw the cutting lines as
marked on the restriction enzyme, then cut your plasmid along those lines.
6. Match up the human DNA with the gene of interest by complementary pairing of the
nitrogenous bases on the ‘sticky ends’. Tape the human DNA in place. You have now made
a recombinant plasmid containing a human ‘gene of interest’!
7. Use the knowledge you have gained in doing this lab, reading your text, and from class notes
to answer the analysis questions.
Analysis Questions:
1. Organisms that contain DNA from two distinctly different organisms are called
_______________________. (1)
2. Scientists have many ways to combine DNA from different organisms. The procedure used
in this lab is ___________________________________________. (1)
3. Plasmids are rings of DNA that are found in _____________________________.
4. Plasmids often give ______________________________________ to a bacterium. (1)
5. ___________________________________ are enzymes that cut DNA at specific places. (1)
This molecules belong to the class of macromolecules called ________________________
(1) and are made in the process of
______________________________________________________________. (1)
6. When you used your scissors to cut the plasmid and the human DNA at the restriction site,
what type of bonds were you breaking?
___________________________________________________________ (2)
7. How are the bonds between sticky ends formed?
___________________________________________________________________________
______________________________________________________________________ (2)
8. How is recombinant DNA technology used in medical science?
___________________________________________________________________________
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9. Name three chemicals made through the process of recombinant DNA cloning and give their
uses in medical science: (6)
1) ______________________________________________________
2) ______________________________________________________
3) ______________________________________________________
Extra Credit (2 points)
Does bacterial DNA contain introns? What implications does this have for the technique
used in recombinant DNA technology?
___________________________________________________________________________
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