Worksheet #16: Chapter 19
List the six main steps needed for a geneticist to find a specific gene in a cDNA library.
1. Have a plate of recombinant bacteria that are expressing recombinant genes.
2. Stamp colonies onto DNA-binding filter paper.
3. Test the clones to find the colony expressing the gene of interest
4. Place the filter paper in a pouch with radioactive-labeled DNA.
5. Clean the filter paper and place under X-ray light.
6. When a match is found, identify the corresponding bacterial colony on the original plate.
A scientist has cut an E. coli plasmid with 2 different restriction enzymes. After examining the fragments by
means of gel electrophoresis, the results are as follows. When the scientist digested the plasmid with Enzyme
A, 1 fragment with length 8 was found. When the scientist digested the plasmid with Enzyme B, 2 fragments
with lengths 5 and 3 respectively were found. When the scientist digested the plasmid with Enzymes A and B,
3 fragments with lengths 5, 2, and 1 respectively were found. Draw a restriction map illustrating the scientist’s
results.
Both enzymes:
since the 5 segment
remained intact,
enzyme A must cut
b/t the two cuts of
enzyme B on the
smaller segment
Enzyme B: 2
cuts : 1st cut =3
(upper part) 2nd
cut = 5 (lower
part)
Enzyme A:
total length = 8
Drawing pictures really helps on these problems!!
The genomes of five individuals were treated with various restriction enzymes. The fragments of DNA were
analyzed by using gel electrophoresis. Which of the individuals are siblings?
A
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B
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C
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D
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E
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Since siblings both inherit exactly half of their genes from Mom and the other half from Dad, the sizes of the
segments will be identical. Therefore, since A and D have identical sized segments, they are siblings.