Fall 1998 Biology 111 Exam #3 - end of genetics + Bioenergetics
There is no time limit on this test, though I have tried to design one that
you should be able to complete within 2.5 hours, except for typing. You
are not allowed to use your notes, old tests, or any books, nor are you
allowed to discuss the test with anyone until all exams are turned in at
9 am on Tuesday November 23. EXAMS ARE DUE AT CLASS TIME ON MONDAY November
23. You may use a calculator and/or ruler. The answers to the questions
must be typed on a separate sheet of paper unless the question
specifically says to write the answer in the space provided. If you do not
write your answers on the appropriate pages, I may not find them unless
you have indicated where the answers are.
Please do not write or type your name on any page other than this cover
page. Staple all your pages (INCLUDING THE TEST PAGES) together when
finished with the exam.
Name (please print):
Write out the full pledge and sign:
How long did this exam take you to complete (excluding typing)?
Lab Questions:
6 pts.
1) Design an experiment using the Ames test to determine whether DDT is
mutagenic or not. You must use two strains of cells and you also want to
determine what affect 30 seconds of UV light might have on DDT's ability
to be mutagenic. Make sure you tell me all the controls you would perform
as well.
Plate 1 = strain one and nothing else (control)
Plate 2 = stain one with 10 µl DDT
Plate 3 = strain one with 50 µl DDT
Plate 4 = strain one with 100 µl DDT
Plate 1 = strain one and nothing else (control)
Plate 2 = strain one and 30 seconds of UV (control)
Plate 3 = stain one and 30 seconds of UV with 10 µl DDT
Plate 4 = strain one and 30 seconds of UV with 50 µl DDT
Plate 5 = strain one and 30 seconds of UV with 100 µl DDT
Plate 1 = strain two and nothing else (control)
Plate 2 = stain two with 10 µl DDT
Plate 3 = strain two with 50 µl DDT
Plate 4 = strain two with 100 µl DDT
Plate 1 = strain two and nothing else (control)
Plate 2 = strain two and 30 seconds of UV (control)
Plate 3 = stain two and 30 seconds of UV with 10 µl DDT
Plate 4 = strain two and 30 seconds of UV with 50 µl DDT
Plate 5 = strain two and 30 seconds of UV with 100 µl DDT
4 pts.
2) Why did some strains have different rates of spontaneous reversion
if they all shared the exact same DNA polymerase alleles? For example,
the spontaneous reversion rate for 1535 was about 20 while 102 was closer
to 250.
Because each strain had a different kind of mutation
(e.g. insertion v. deletion v. base substitution), the same DNA polymerase
must be more prone to make the type of mutation in strain 102 than the type
in strain 1535. From this, we should be able to determine the relative tendency
of DNA polymerase to make different types of mutations.
Lecture Questions:
6 pts.
3) a) What is a restriction enzyme made of?
It is a protein, so it is made of amino acids.
b) What is its substrate?
Its substrate is DNA, and a particular sequence of
bases, depending on the enzyme.
c) What is the product?
The product is restricted, or cut, DNA so that the
phosphodiester backbone is cut on both strands. This results in one piece
of DNA becoming two pieces.
6 pts.
4) What is the molecular cause for HD?
There is a trinucleotide repeat that causes too many
copies of an amino acid in a row. This causes the huntingtin protein to
bind too tightly to HAP-1 but why that causes the disease is unclear. We
do know that the more repeats a person has, the sooner the disease will
be evident.
10 pts.
5) Generate a genetic linkage map from these data about a dominant disease:
142 individuals were AA and had only the upper band
9 individuals were AA but had both bands
11 individuals were aa but had both bands
138 individuals were aa and had only the lower band
a) How many people had the disease?
149 have the disease plus any heterozygotes not listed
above.
b) What is the map distance between the disease locus and the RFLP locus?
6.7 map units
c) What would you tell a couple whose fetus was tested and had only the
lower band?
I would tell them that there is only a 0.4% (6.7%
times 6.7%) chance that their child will not have this disease.
4 pts.
6) Why did investigators need to do chromosomal walking if they could
use cDNA as a probe for CF or exon amplification for HD? Why not skip over
chromosomal walking since it takes so long?
They had to narrow down the number of possible restriction
fragments that they wanted to probe. Since they could not probe or do exon
amplification on every restriction fragment in a genomic library, they needed
a way to eliminate most of the DNA that was not between the RFLPs that were
known to flank the disease locus.
4 pts.
7) If chlorophyl a (the pigment in the reaction center) can only absorb
blue and red light, then why don't leaves look orangy-yellow?
There are other pigments that absrob in the yellow
orange range so the only light that bounces back is the green light which
is not absorbed.
6 pts.
8) Define (as positive or negative) the DG, DH
and DS of the light reaction.
DG = positive
DH = positive
DS = negative
6 pts.
9) Tell me what the 3 final products of the light reaction are and how each
is produced.
ATP is produced
when the H+ gradient (produced when electrons are transported
in the first half of non-cyclic electon flow and the cyclic electron flow)
is used as an energy source. The H+ ions pass through the ATP
synthase which produces ATP.
NADPH is produced when NADP+ is the final electron acceptor
for the second half of non-cyclic electron flow.
Oxygen is produced as a waste product when water is split to provide
two electrons to fill the hole in PSII after chlorophyll a
has been photooxidized.
8 pts.
10) What is consumed in the dark reaction and what is produced?
.ATP, NADPH, and CO2 are consumed.
Fixed carbon, in the form of glyceraldehyde-3-phosphate is produced.
4 pts.
11) In this reaction, is this molecule being oxidized or reduced? To get
credit, you must explain your answer.
The molecule is being oxidized. You can tell this because the carbons have less hydrogen associated with them and more oxygen.
4 pts.
12) What role does Rhizobium play in the life of a soy bean plant?
It fixes nitrogen so that the plant can absorb it
in a reduced molecule.
Is nitrogen fixation reduction or oxidation when ammonium is produced?
Explain.
Ammonia has more hydrogens associated with it which
is indicative of reduction.
8 pts.
13) List all the different reducing agents produced during cellular respiration
and how much is produced from one glucose molecule.
One glucose produces 10 NADH molecules and
2 FADH2 molecules.
List the processes within cellular respiration which produce these reducing
agents.
Glycolysis produces
2 NADHs.
"Pre-citric acid cycle" produces 2 NADHs.
Citric acid cycle produces 6 NADHs and 2 FADH2.
6 pts.
14) Plants consume water, CO2, and O2. Where and why
are each of these consumed?
Water is consumed
in the light reaction, as explained in number 9 above. It is also consumed
in the citric acid cycle of cellular respiration.
CO2 is consumed in the dark reaction when the carbon is
reduced into glyceraldehyde-3-phosphate.
O2 is consumed during oxidative
phosphorylation, during cellular respiration.
We do not consume one of these three, which one and why?
We cannot fix carbon, therefore we do not consume
CO2. We do need water.
6 pts.
15) What is cyclical about the citric acid cycle? Explain in general terms
how carbons cycle through this pathway.
The fact that a four carbon sugar joins with the acetyl
group from acetyl-CoA and the two carbons on the acetyl group are processed
into 2 CO2s, leaves the same four carbons back in their original
form to be recycled again. What goes around comes around (i.e. 4 carbons).
6 pts.
16) List the three carbon-based products of fermentation, excluding
ATP and NAD+.
CO2
and ethanol are produced by fermentation.
Lactic acid is also produced by fermentation.
Which one or ones do you think Clostridium tetanii produces in
us and why?
Lactic acid, since we do not tend to produce bubbly
alcohol in our tissue when infected with the bacterium.
4 pts.
17) Facultative anaerobes need a control mechanism that repsonds to the
presence or absence of oxygen. Develop a reasonable hypothesis which describes
how such an organism can switch from anaerobic metabolism to aerobic. There
are several correct answers to this question but keep your answer short
and limited to only one hypothesis. Note that it is worth only 4 points.
Many possible answers here.
2 pts.
18) Why would anaerobic bacteria not be harmed by either cyanide or paraquat?
Since they do not have an electron transport systems,
there would not be any harm or loss of energy.
+2 pts possible but no points lost
Bonus Question:
Why do people get dizzy when their blood glucose level drops even though
there is plenty of protein and lipids available for catabolism in the brain?
Brain cells cannot metabolize anything but glucose,
so they run out of energy when glucose levels drop. They cannot convert
the other molecules into products that can enter cellular respiration (glycolysis
and Krebs).