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page 1 of 6 pages
MOLECULAR BIOLOGY
BIO372S
January 31, 2013
First mid-term examination
(one hour)
Please read each question carefully and put your answers on the exam
page only in the spaces indicated.
Good luck!
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Student Number:
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well
10,000 bp
100
bp
1 (15 points). You are given
a sample of double-stranded
DNA containing the following
fragment lengths: 100, 316,
1000, 3162, 10000, 15000, and
20000 bp. The 1% agarose gel
is run so that the smallest
fragment appears at 9 cm from
the well and the 10000 base
fragment 3 cm from the well.
Show the approximate
positions of the other
fragments.
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page 3 of 6 pages
2 (15 points). Put check marks below for the conditions that apply to
transcript mapping.
S1 mapping
of 5’ end
5’ end of DNA
probe is labeled
3’ end of DNA
probe is labeled
accurate to
a single
nucleotide
Polynucleotide
kinase
Used
Klenow
fragment of
DNApol used
S1 nuclease
used
Electrophoretic
mobility of DNA
is measured
Electrophoretic
mobility of RNA
is measured
Measures transcript
start site
Measures transcript
stop site
S1 mapping
of 3’ end
Primer extension
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page 4 of 6 pages
3 (20 marks). You make an equal mixture (by weight) of: i) E.coli DNA
and ii) the unique fraction of Agaricus bisporus DNA. The two DNAs
were previously sheared to a uniform size of 200 bp. The DNA mixture
was thermally denatured and then placed in standard conditions
allowing renaturation. Draw a plausible renaturation (Cot) curve.
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page 5 of 6 pages
4 (30 points). The following question is in reference to the Meselson
and Stahl experiment. Cells of E. coli are grown on a medium
containing the heavy isotope of nitrogen (15N) which is incorporated
into the DNA, which is of higher than normal density. The cells are
then transferred to medium with the normal, lighter isotope of
nitrogen (14N). After various periods of time, DNA is extracted and
analysed with cesium density-gradient centrifugation. Show the banding
positions, and their relative intensities, over four generations after
the transfer to the medium with the lighter isotope of nitrogen.
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page 6 of 6 pages
5 (10 points). Below is a melt curve of a sample of DNA. Show a
plausible corresponding density trace from cesium-chloride density
gradient centrifugation for the same DNA.
Melt curve
Density trace
6 (10 Points). Below is a nucleotide sequence of DNA. Write a
plausible sequence after RIP in Neurospora crassa has acted upon it.
5’GTCTTTACTAGGCATTGGCAGTTATACAGGCATTTGGGCTATCATTT 3’
Sequence after RIP here: