Download Multiple Choice - 30 points total In each of the questions, select the

Multiple Choice -
30 points total
In each of the questions, select the answer which you believe is most nearly correct. If more than
one answer seems to be correct, pick the single answer you believe to be the best.
1)
B or D
How many chromatids would be present at metaphase of the
second meiotic division of an organism with a diploid number of 12 (2N = 12)?
A) 6
B) 12
C) 18
D) 24
E) 48
2)
D
(An SAT-style analogy question): Which of the following words, when
placed into the blank space, best completes the analogy?
sugars are to polysaccharides as ____________ are to nucleic acids.
A) deoxyriboses
B) nitrogenous bases
C) amino acids
D) nucleotides
E) nucleosomes
3)
A
Which of the following statements is true about the β-sheet structure pattern of
polypeptide folding?
A) It is stabilized by hydrogen bonds between adjacent β-sheets
B) It is stabilized by hydrogen bonds within a single β-sheet
C) It is stabilized by hydrogen bonds between R-groups
D) It is one of the most important forms of primary structure in proteins
E) None of the above
4)
C
Many enzymes have two distinct shapes, or conformations, an active one in
which it binds substrate, and an inactive one, in which it does not. A compound that
stabilized the inactive conformation of an enzyme would most likely be:
A) An activator
B) A competitive inhibitor
C) A non-competitive inhibitor
D) A prosthetic group
E) None of the above
5)
D
All nucleotides contain:
A) An amino group, a carboxyl group, and an R-group
B) A prosthetic group, a ribose sugar, and a disulfide bond
C) A nitrogenous base, a peptide bond, and an R-group
D) A 5-carbon sugar, a phosphate group, and a nitrogenous base
E) Deoxyribose, phosphate, and adenine
Biology 200 – 2010
2nd Exam Answer Key
6)
B
Actin and myosin are proteins associated with:
A) DNA replication
B) The cytoskeleton
C) The electron transport chain
D) Glycolysis
E) The eukaryotic nucleus
7)
E
Which of these statements about the C4 photosynthetic pathway is true?
A) C4 plants do best under relatively low light intensities
B) C4 plants are more efficient because they require fewer ATP molecules to run the
Calvin cycle
C) C4 plants don't use the Calvin cycle at all, and produce carbohydrate using a radically
different pathway
D) C4 plants release less O2 than C3 plants
E) None of the above
8)
B
Which of the following statements about the α-helix pattern of protein folding is
not true?
A) α-helix is a form of secondary structure
B) The α-helix is stabilized by disulfide bonds
C) The α-helix may form part of the active site of an enzyme
D) α-helices involve hydrogen bonds between oxygen and hydrogen atoms.
E) Proteins with quaternary structures may contain α-helical regions
• As you know, James Watson first saw Franklin's "B-form" pattern of DNA in
February 1953. When he returned to Cambridge, the first model that he
developed was a "like-with-like" base-paired model (sketch at right). Watson
wrote: “If this was DNA, I should create a bombshell by announcing its
discovery." Questions 9 & 10 refer to the like-with-like model.
9)
D
Among the key properties of DNA that this like-with-like model
would explain is:
A) Its helical diffraction pattern
B) DNA replication
C) The placement of sugar-phosphate chains on the outside of the
molecule
D) All of the above
E) None of the above
10)
A
Watson and Crick quickly abandoned the like-with-like model. Among the
reasons they dropped it were:
A) It failed to explain Chargaff’s rule
B) Hydrogen bonds could not be drawn between any chemical forms of the bases
C) X-ray data confirmed that the bases were actually on the outside
D) All of the above
E) None of the above
Page 2
Biology 200 – 2010
2nd Exam Answer Key
11) The Peptide Bond (12 points)
Show below are the structures of two important amino acids (glycine & glutamate).
Glycine
Glutamate
First, circle the alpha-carbons in each amino acid. Then, draw the structure of the dipeptide Nglu-gly-C. (You may abbreviate some of the chemical groups, such as NH2 or COOH. But be
sure to show each atom and each bond clearly in the region of the peptide bond):
Grading (12 points total):
+2 points for correct order of amino acids
+2 points for correct ID of alpha carbons (-1 for mistake in either)
+8 points for correct peptide bond
(No deduction for minor errors outside of the shaded peptide bond region)
Page 3
2nd Exam Answer Key
Biology 200 – 2010
12) Genetics (18 points)
Feather color in parakeets is determined by a two gene system,
with one gene controlling blue pigment and the other yellow
pigment. Each gene has two alleles, one of which results in
pigment production, and one of which does not. The pigmentproducing allele displays simple dominance in each case.
Use this notation for the
feather color alleles:
Gene 1
Gene 2
Y = yellow
B = blue
y = no color
b = no color
A) Two green parakeets (which have both yellow and blue pigment in their feathers) are crossed.
Over 13 years, this mating pair have produced 58 offspring, all of which were green, just like
their parents. One possibility, shown below, is that both parents are homozygous dominant
(genotype YYBB). That is shown below as Possibility #1. Is that the only possibility? If yes,
write “Yes” in the space below. If not, list all other possible genotypes in the same format as
possibility #1:
Possibility #1:
Other possibilities:
BBYY and BBYY
BBYy and BbYY
+2 points
BBYY and BbYy
+2 points
BBYY and BBYy
+2 points
BBYY and BbYY
+2 points
(8 points total. Deduct 1 point for any incorrect genome pair)
B) You decide to try checking among possible genotypes by doing a cross between two of their
grown offspring. In their first clutch, they lay three eggs, which hatch into a white parakeet and
two green ones. What are the genotypes of the parents of these 3 new birds? (No reasoning
needed – just write down the genotypes)
BbYy and BbYy
+4 points
(Note: These are the only possible genotypes that would carry a green phenotype and still be
capable of producing white offspring)
C) If we continue to breed the two parakeets in Question B to produce a large number of
offspring, what sort of feather color ratios would we expect among their offspring? Use a
Punnett square, or a clearly written calculation of probabilities to support your argument.
BY
By
bY
by
BY
BBYY
BBYy
BbYY
BbYy
By
BBYy
BByy
BbYy
Bbyy
bY
BbYY
BbYy
bbYY
bbYy
by
BbYy
Bbyy
bbYy
bbyy
Their offspring should display a 9:3:3:1 ratio:
Green (9) Blue (3) Yellow (3) White (1)
Grading (6 points total):
+3 points for Punnett square (or, probability calculation)
+3 points for 9:3:3:1 ratio
Page 4
Biology 200 – 2010
2nd Exam Answer Key
13) Metabolism (20 points)
A) A culture of yeast grown under aerobic conditions using glucose as an energy source is currently
producing 20 microliters of CO2 per minute. If oxygen is suddenly removed, switching the culture to
anaerobic conditions (still using glucose), what will be the approximate rate at which CO2 is now
produced by the culture if it maintains the same rate1 of ATP production?
Make a specific numerical prediction in terms of microliters of CO2 per minute (in other words, write
down a number), and then explain your reasoning:
Grading (8 points total):
Reasoning:
• Metabolism will switch to fermentation
+2 points
• Rate of glucose utilization will increase ~ 18 times as a result
+2 points
• However, now each glucose results in just 2 CO2 released, instead of 6 per glucose
from aerobic pathways.
+2 points
• Numerical Prediction: rate = 20 microliters * 18 / 3 = 120 microliters +2 points
B) A culture of yeast cells identical to the one in part (A), also currently producing 20 microliters of CO2
per minute, is treated with Mitoporin XJ-12, an experimental drug that renders their inner mitochondrial
membranes completely permeable to H+ ions. Oxygen is still present. What will be the approximate rate
at which CO2 is now produced by the culture if it maintains the same rate of ATP production?
Make a specific numerical prediction in terms of microliters of CO2 per minute and explain your
reasoning.
Grading (8 points total):
Reasoning:
• With no H+ gradient, ATP synthase stops working
+2 points
• Rate of glucose utilization will increase ~ 9 times as a result
(since only 4 ATPs are now produced per glucose)
+2 points
• Unlike part (A), 6 CO2 molecules are still released per glucose. +2 points
• So, rate = 20 microliters * 9 = 180 microliters
1
+2 points
Nothing tricky here. All that is meant is that the cells continue to produce the same number of ATP molecules per
minute, except that now they do it anaerobically.
Page 5
Biology 200 – 2010
2nd Exam Answer Key
C) In order to investigate the role of oxygen in the Krebs cycle, you are about to carry out
experiments in which radioactive oxygen (18O) will be supplied to a culture of yeast cells grown
under aerobic conditions with glucose as an energy source. In the first few minutes2 after 18O is
introduced to the cells, approximately what % of the CO2 released from the culture will contain
18O? Explain this estimate in one or two sentences.
Grading: 4 points total
The Estimate: Zero %.
+2 points
Reasoning:
O2 is used as an electron acceptor, and water will become labeled with
18
O, not CO2.
Or, The oxygen in CO2 comes from glucose or water, not from atmospheric oxygen.
+ 2 points for either line of reasoning
2
Nothing tricky here, either. Eventually, that radioactively-labeled oxygen will get into every molecule that
contains oxygen atoms. But what I’m asking here is how much of it will go immediately and directly into the CO2
released from the cells.
Page 6
2nd Exam Answer Key
Biology 200 – 2010
14) Gene Mapping
(20 points)
You are investigating the genetics of two truebreeding lines of Drosophila melanogaster.
Each line is homozygous for three autosomal
genes controlling wing appearance.
Line 1: Red, Normal-Shaped, Transparent
Wings
Line 2: White, Curly-Shaped, Opaque Wings.
• Thirty flies from Line 1 are mated to thirty flies from Line 2, and their F1 offspring (all 4,637
of them) display the following traits:
100%: white, normal-shaped, transparent wings
From these results you advise your research supervisor that the alleles producing white, normalshaped, and transparent wings are dominant (you label these alleles W, N, and T). Obviously,
red, curly-shaped, and opaque wings are recessive (w, n, and t).
Your advisor, dazzled with your prowess, assigns an assistant to produce a line of flies with red,
curly-shaped, and opaque wings. You mate these flies to your F1 flies, and obtain the following
F2 results from 1,000 total offspring:
#
wing phenotype
382
8
38
401
41
56
12
62
wNT
wNt
WNt
Wnt
wnT
WNT
WnT
wnt
Notation:
Symbols in the table at left refer only to
the phenotypes of the F2 flies. For
example, " "382 wNT" means that 382
flies had red, normal-shaped transparent
wings. Likewise, "8 wNt" means that 8
flies had red, normal-shaped, opaque
wings, etc....
a) Calculate recombination frequencies between each of these three pairs of genes (circle each of
the recombination frequencies so that the grader can locate them)
The parental combinations of alleles (from the two lines) are:
wNT
&
Wnt
Recombination rates:
W and N:
38 + 41 + 56 + 62 = 197 / 1000 = 19.7% or 0.197
W and T:
8 + 56 + 12 + 62 = 138 / 1000 = 13.8% or 0.138
N and T:
8 + 38 + 41 + 12 =
99 / 1000 = 9.9% or 0.099
Grading: Award +4 points for each correct frequency (max. total: 12 points)
Page 7
Biology 200 – 2010
2nd Exam Answer Key
• question 14, continued:
b) Draw a genetic map for the location of each of these three genes and their relative distances
from each other. If one or more of the genes are unlinked, show that on the map. (please circle
the map so that the grader can locate it).
T
W
N
0.099
0.138
Grading: +8 points for correct map
• Deduct 4 points for a map in which gene order is correct, but in which gene T is shown closer
to W than to N.
(it's only necessary to show the recombination frequencies between neighboring genes, although it's also
OK to show the frequency between the most distant genes)
Also: Full credit awarded for correctly mapping any recombination frequencies calculated — even
incorrect ones — in part a.
Page 8