Download Answers to Exam 2 multiple choice and TF questions

Biol 205 Exam 1 TEST FORM A
Spring 2008
NAME___________________________________
• On Side 2 of your SCANTRON SHEET fill in your ID number and be
sure to indicate TEST FORM A
• The answers to Part I multiple choice and true-false questions should be
placed on the SCANTRON SHEET.
• The answers to Part II should be written directly on the exam.
• NO CALCULATORS OR CELL PHONES ALLOWED.
• No sending or receiving signals of any kind.
Score
Part I
Scantron (40 pts.)
Part II
1 ( 12 pts.)
2 ( 16 pts.)
3 ( 12 pts)
Total out of 80 pts
Part I: Multiple choice Questions. 2 pts. each.
ONE CORRECT ANSWER for each question
1. The advantage to the cell of the gradual oxidation of glucose compared with its
combustion to CO2 and H2O in a single step is that
a. more free energy is released for a given amount of glucose oxidized.
b. no energy is lost as heat.
c. energy can be recaptured in a usable form.
d. more CO2 is produced for a given amount of glucose oxidized.
e. less O2 is required for a given amount of glucose oxidized.
2. Which of the following steps or processes in aerobic respiration include the production of
carbon dioxide? THIS QUESTION OMITTED – everyone received two points
a. Glycolysis
b. Conversion of pyruvate to acetyl CoA
c. The citric acid (Krebs) cycle
d. Both a and b are correct
e. Both a and c are correct
f. Both b and c are correct
1
3.
a.
b.
c.
d.
e.
This figure illustrates:
coupled endergonic-exergonic reactions
an exergonic reaction that would only proceed if coupled to an endergonic reaction
an exergonic reaction that would only proceed at a high rate in the presence of a catalyst
an endergonic reaction that would only proceed at a high rate in the presence of a catalyst
none one of these statements is correct.
4. Recall the paper on unusual humans with mutations in the Y-linked SRY gene. Which
statement is false?
a. Proteins that function in the nucleus are translated in the cytoplasm and then exported to the
nucleus through nuclear pores
b. Humans with defects in the function of the SRY protein often have an XY genotype but
feminized phenotype (female gonads).
c. Since the SRY protein regulates the transcription of genes required for testes formation, it
must function in the nucleus where it binds with DNA.
d. The mutation in SRY that was described in this paper results in a protein that can perform its
transcriptional regulatory function, but which is mis- exported into the mitochondria rather than
into the nucleus.
5. Based on chemical structure, which of the molecules listed below is not likely to be a
molecular remnant of the ancient RNA world?
a. the ribozyme that catalyzes peptide bond formation
b. NADH
c. any molecule derived from a ribonucleotide
d. an amino acid
e. ATP
6. RNA polymerase
a. requires an RNA primer to begin transcription.
b. does not require the DNA double helix be unwound for transcription.
c. hydrolyzes nucleotides to their di-phosphate form (e.g., ADP) plus Pi.
d. synthesizes RNA in a 5’ to 3’ direction.
e. reads the DNA template in a 5’ to 3’ direction.
2
7. Glycolysis is a process that
a. generates the majority of ATP in a cell that uses aerobic respiration.
b. involves the stepwise oxidation of sugars to yield ATP and NADH.
c. involves the stepwise oxidation of sugars in the mitochondria to yield energy in the form of
ATP.
d. requires NADH as a reactant to provide electrons to reduce sugars.
CHOOSE TRUE OR FALSE.
• Place your answers directly on the Scantron Sheet
• Answer FALSE if any part of the statement is incorrect or if the second part of the
statement does not follow logically from the first part.
• If there are two statements, the first statement is true and you are to determine whether
the second statement is true or false.
• 2 PT for each question
8. T F If the mechanism that normally senses tension across two sister chromatids (in
metaphase of mitosis) is defective, then the products of mitosis of a 2n cell may end up with
copies of both the maternal and paternal homolog.
Second part of statement does not follow logically from the first as the products of mitosis of a 2n
cell should always have a paternal and maternal homolog
9. T F Only aerobic organisms use glycolysis to degrade sugars, suggesting that glycolysis
evolved rather recently.
10. T F Some thermodynamically favorable (spontaneous) reactions that occur in cells require
a catalyst but most do not.
11. T F Oxidation of a molecule requires the removal of electrons and can occur even if there is
no oxygen directly involved in the reaction.
12. T F One turn of the citric acid cycle generates two molecules of CO2.
13. T F The trigger molecule for RNAi is an RNA-DNA duplex (double-stranded polymer of
RNA H-bonded to DNA) since this type of molecule is not typically found in the cytoplasm of a
cell and thus indicates the presence of rogue nucleic acids.
14. T F Acetyl CoA is synthesized from pyruvate and CoA in a reaction that also generates
NADH and carbon dioxide
15. T F The drug taxol binds to the plus end of microtubules and prevents loss of subunits
from this end; in contrast the drug colchicine prevents addition of subunits to the plus end.
Despite their opposite effects, both compounds would prevent cells from moving normally
through mitosis.
3
16. T F Microtubules nucleate (form) at the centromeres and then connect to kinetochores,
which are structures found at the centrosome region of the sister chromatids.
NOTE that the terms centrosome and centromere are misused.
17. T F During metaphase of mitosis, kinetochores that are not attached to the positive end of a
microtubule send a message that reads (in a molecular form): “Put anaphase on hold, I am not
attached.”
18. T F Prokaryotic cells do not undergo mitosis because there is no need to ensure the
duplicated chromosome is parcelled out evenly to the daughter cells.
19. T F Since haploid organisms (organisms whose conspicuous phase is haploid) are 1n, they
cannot ever undergo sexual reproduction.
20. T F See figure below. During anaphase of mitosis the movement of interpolar
microtubules relative to each other is orchestrated by molecular motors that carry one
microtubule as cargo and walk to the plus end of the other microtubule.
Part 2 follows on next page
4
Part II: Write your answers to these questions directly
on the exam
Step 1 in this figure
shows the elongation
step in translation
immediately after an
incoming aminoacyltRNA (charged) has
bound to the
ribosome.
1. ( 12 pts. TOTAL)
a. (2 pts.)
On Step 1: label the 5’ and 3’ ends of the mRNA.
b. (2 pts.)
On Step 1: label the P and A sites (draw an arrow and indicate by A or P)
c. (8 pts.)
On Step 2, draw in the tRNAs and the amino acids that are shown in Step 1.
Use the same symbols and labelling as shown in step 1. You do not need to
provide a key to the symbols.
5
2. ( 16 pts.)
PART A Multiple choice 3 pts. One correct answer – circle directly on exam.
Choose the best restatement of Muller’s rachet:
a. Since mitosis is a conservative cell division process, genomes that are propagated solely by
mitosis should not accumulate mutations and therefore will not undergo genetic decay
b. Genomes that are propagated solely via asexual reproduction are susceptable to the
accumulation of weakly deleterious mutations.
c. Individual chromosomes cannot be susceptible to Muller’s rachet if they are propagated via
meiosis.
d. Dominant mutations that dramatically reduce the fitness of an individual will not accumulate
in the genomes of sexually reproducing organisms.
PART B (13 pts) On the next page, draw a diagram that illustrates how the process of meiosis
helps to “cleanse” a genome of mutations.
READ THROUGH THESE INSTRUCTIONS CAREFULLY
Consider a diploid (2n) cell of genotype AaBb. The uppercase alleles of each gene are wildtype. The lowercase alleles are mutant. Draw a diagram showing the mating of individuals of
genotype AaBb X AABb that illustrates why sexual reproduction is so great in the context of
genome decay (Muller’s rachet).
• ONLY illustrate one mechanism of recombination: EITHER independent assortment
OR crossing over NOT BOTH
• Label homologs, sister chromatids and be sure that the alleles of each gene are clearly
and appropriately placed on the chromosomes.
• For the AaBb parent, draw out the chromosomes in metaphase I and clearly indicate
recombination events that are directly relevant to this question. Don’t draw out any
other stages, but clearly indicate the genotypes of the final meiotic products of the
specific metaphase I that you have drawn.
• Do not show meiosis for the AABb parent but indicate possible gamete genotypes.
• Be sure to generate a 2n offspring from the appropriate meiotic products of each parent
and indicate the gentoype of this offspring. NOTE: do not indicate all possible genotypes
– just one that is directly relevant to this problem.
• Don’t clutter your diagram with cytoskeletal elements
PUT your diagram on THE next page
6
Your diagram should illustrate only one of these processes. Do not try to show both
mechanisms. Indicate your choice with a check mark:
 INDEPENDENT ASSORTMENT
 CROSSING OVER
7
3. (12 pts. total) After biochemists discovered the first 5'  3' DNA polymerase, they
predicted that cells would also have 3'  5' DNA polymerases and exerted considerable effort
looking for one.
a. (2 pts.) What is meant by 5'  3' polymerization?
b. (10 pts.) Draw a diagram illustrating why 3’  5’ polymerase was expected to exist. Your
answer should consist of
• a clearly labelled diagram of a replication fork
• the 3’ and 5’ ends of ALL strands should be clearly indicated
• template strands and daughter strands should be clearly labelled
• a caption (insisting of 1-2 sentences that explains your diagram) should be included and
the rolls of the two different types of polymerases should be indicated
• NOTE: I am NOT asking how DNA replication actually occurs, but how
the biochemists anticipated it should occur.
8