Practice Midterm II Answer Key
**Extended version with answer explanations
1. During mitosis, the chromosomes line up in the middle of the cell during which phase:
A. Anaphase
B. Prometaphase
C. Telophase
D. Prophase
E. Metaphase
See Lecture 13. In this state, the mitotic spindle is fully formed, there nuclear envelope is gone, and the
chromosomes line up on an imaginary line along the metaphase plate.
2. During mitosis, the first point at which the nuclear envelope disintegrates allowing microtubules to attach to
kinetochores is during which phase:
A. Anaphase
B. Prometaphase
C. Telophase
D. Prophase
E. Metaphase
See Lecture 13. During this stage the mitotic spindle is fully formed and the centrosomes are at opposite poles. The
nuclear envelope disintegrates. At this stage, the chromosomes are in their most condensed form.
3. During mitosis, sister chromatids begin to separate during which phase:
A. Anaphase
B. Prometaphase
C. Telophase
D. Prophase
E. Metaphase
See Lecture 13. During Anaphase, the MT start to have a tug of war, pulling the chromosomes apart. There’s an
enzyme called separase that cleaves the cohesion protein that keeps the sister chromatids together. The
chromosomes are then drawn to opposite poles. There is no nuclear envelope at this stage.
4. To be active a protein kinase that regulates cell cycle must be attached to _______.
A. Tubulin
B. Cyclin
C. G1 checkpoint
D. MPF
E. Cdk
See Lecture 14. Active, protein kinase must be attached to a cyclin. Thus, they are known as cyclin-dependent
kinases or Cdks.
5. MPF is the combination of a cyclin and __________________.
A. Tubulin
B. G2 checkpoint
C. Protein kinase
D. Actin
E. Cdk
See Lecture 14. MPF= cyclin + cyclin-dependent kinase (Cdk)
6. The combination of a cyclin protein and a protein kinase is called a ______________, which is involved in regulating
the cell cycle.
A. Oncogene
B. G2 checkpoint
C. G1 checkpoint
D. Tumor suppressor gene
E. Cdk (Better answer is MPF)
See Lecture 14. MPF= cyclin + cyclin-dependent kinase (Cdk). A protein kinase must be attached to a cyclin and
that’s why they’re referred to as cyclin-dependent kinases. When they’re attached, they combine to form MPF>
7. One hallmark characteristic of a cancer cell is:
A. Anchorage dependence
B. Normal cell cycle control
C. Anchorage independence
D. Expression of proto-oncogene
E. Density-dependent inhibition
See Lecture 14. Cancer cells lack the ability for anchorage dependence (hence anchorage independence) and they
lack the ability for density-dependent inhibition. Normal cells have the ability for anchorage dependence and
density-dependent inhibition.
8. You are an evil mastermind and wish to create a virus that will infect cells and transform them from normal cells into
tumor (cancerous) cells. What method would you choose?
A. create a virus that expresses a proto-oncogene
B. create a virus that expresses a G1 checkpoint protein
C. create a virus that expresses an oncogene
D. create a virus that expresses a tumor suppressor gene
E. create a virus that expresses a G2 checkpoint protein
See Lecture 14. An oncogene is a gene found in viruses or as part of the normal genome that is involved in triggering
cancerous characteristics. They drive the cell cycle progression nonstop so that cells constantly divide. A tumor
suppressor gene on the other hand, inhibits cell division. You’d have to mutate a tumor suppressor gene remove
the inhibitory signaling of cell cycle to uncontrollably increase cell division.
9. What kinds of mutations can convert a proto-oncogene into an oncogene?
A. gene amplification
B. point mutation within a gene
C. chromosomal translocation
D. A and B
E. A, B, and C
See Lecture 14.
10. _________________________ separate during Meiosis I.
A. chiasmata
B. sister chromatids
C. homologous chromosomes
D. kinetochore microtubules
E. diploid cells
See Lecture 15. Homologous chromosomes separate during Meiosis I.
11. _________________________ separate during Meiosis II.
A. chiasmata
B. sister chromatids
C. homologous chromosomes
D. kinetochore microtubules
E. diploid cells
See Lecture 15. Sister chromatids separate during Meiosis II. This closely resembles Mitosis.
12. What type of cells are produced following Meiosis I?
A. two diploid cells, each with identical genetic material
B. two haploid cells, each with identical genetic material
C. two haploid cells, each with distinct genetic material
D. two diploid cells, each with distinct genetic material
E. four haploid cells, each with distinct genetic material
See Lecture 15. At the end of Meiosis I, two haploid cells are formed. Each chromosome still consists of two sister
chromatids.
13. One major feature of meiosis is the genetic variability that is generated. What mechanisms do you think would
generate the most variability together?
A. imprinting and crossing over
B. independent assortment and genomic imprinting
C. random fertilization and independent assortment
D. independent assortment and crossing over genomic
E. crossing over and random fertilization
See Lecture 15. Because of independent assortment alone, you get 223x223 combinations! Add that with random
fertilization (~250 million sperm per 1 egg) and you can have 70 trillion combinations!
14. For your birthday, you received a purple flowering pea plant. However, the friend that gave it to you did not know
its genotype. You know you can figure it out by crossing it to a homozygous recessive white flowering (pp) pea plant.
After performing the cross, you end up with 1⁄2 of the offspring having purple flowers and 1⁄2 the offspring having
white flowers. What is the genotype of the plant you received for your birthday?
A. PP
B. pp
C. Pp
D. impossible to determine
See Lecture 16. If your plant was PP, all offspring crossed with a pp would have a Pp genotype and all would be
purple. Your plant had a Pp genotype because crossing with a homozyogous recessive would result in ½ purple (Pp)
and ½ white (pp).
15. For your birthday, you received a purple flowering pea plant. However, the friend that gave it to you did not know
its genotype. You know you can figure it out by crossing it to a homozygous recessive white flowering (pp) pea plant.
After performing the cross, you end up with all of the offspring having purple flowers. What is the genotype of the
plant you received for your birthday?
A. PP
B. pp
C. Pp
D. impossible to determine
See Lecture 16. Your plant was PP, so all offspring crossed with a pp would have a Pp genotype and all would be
purple. If your plant had a Pp genotype, crossing with a homozyogous recessive would result in ½ purple (Pp) and ½
white (pp).
16. What provides energy for electrons to increase in potential energy to move from water to glucose?
A. ATP
B. solar energy
C. chlorophyll
D. kinetic energy
See Lecture 12. Redox equation for photosynthesis:
Solar (Light) Energy + carbon dioxide + water  glucose + oxygen
17. An electron’s potential energy level is dependent on:
A. the charge of the electron
B. Whether the atomic nucleus is positive or negative
C. how far away the electron is from the nucleus
D. whether the electron is oxidized or reduced
See Lecture 11; Figure 2.6. An electron’s potential energy level is dependent upon how far away it is from the
nucleus. The negative charge of electron is attracted to positive charge of the nucleus.
18. Which of the following statements is true about enzyme-catalyzed reactions?
A. The reaction is faster than the same reaction in the absence of the enzyme.
B. The free energy change of the reaction is opposite from the reaction that occurs in the absence of the enzyme.
C. The reaction always release energy.
D. Enzyme-catalyzed reactions require energy to activate the enzyme.
E. Enzyme-catalyzed reactions release more free energy than non-catalyzed reactions.
See Lecture 10. Enzymes catalyze (accelerate) reactions by lowering the activation energy barrier enabling the
reactant molecules to absorb enough energy to reach the transition state even at moderate temperatures.
19. How is ATP generated in cells without mitochondria?
A. Calvin Cycle
B. Transport of ATP from other cells
C. Substrate-level phosphorylation
D. The electron transport chain
See Lecture 11. In substrate-level phosphorylation, an enzyme has a substrate with a phosphate group attached to
it. This enzyme pops that phosphate group off and adds it to ADP to form ATP. This can occur in the absence of
oxygen.
20. Choose the two main inputs into the Calvin cycle:
A. CO2 and ATP
B. NAD+ and ATP
C. NADH and ADP
D. NAD+ and CO
See Lecture 12. For the Calvin Cycle (dark reactions) the inputs are CO2, ATP, NADPH and RuBP. What are the
outputs?
21. In the cross PpRRYy X PpRrYY, what fraction of the offspring will have white flowers and round, yellow seeds? (P =
dominant allele for purple; R = dominant allele for round; Y = dominant allele for yellow)
A. 3⁄4
B. 1⁄2
C. 1⁄4
D. 3/8
E. 5/8
See Lectures 16 and 17. Look at each genotype separately. If you cross Pp x Pp, you have a ¼ chance of getting
white. An RR x Rr cross will give you 4/4 chance of getting round. For Yy x YY, you’ll have a 4/4 chance of getting
yellow. ¼ x 1 x 1 = ¼
22. In the cross ppRrYy X PpRrYy, what fraction of the offspring will have white flowers and round, green seeds? (P =
dominant allele for purple; R = dominant allele for round; Y = dominant allele for yellow)
A. 3⁄4
B. 3/8
C. 5/16
D. 5/32
E. 3/32
See Lectures 16 and 17. A pp x Pp cross will give you ½ probability of white flowers. An Rr x Rr cross will give you a ¾
chance of round seeds and a Yy x Yy cross will give you a ¼ chance of green seeds. ½ x ¾ x ¼ = 3/32
23. If the genes for seed color (Yellow/green) and seed shape (Round/wrinkled) are on the same chromosome, and no
crossing over occurs between the two genes, what would your phenotypic ratios be for the YyRr X YyRr cross?
A. 1:2:1
B. 9:3:4
C. 3:1
D. 9:3:3:1
See Lecture 16. They undergo ‘dependent’ assortment since they are on the same chromosome.
24. Paracrine signaling:
A. Involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
B. requires nerve cells to release a neurotransmitter into the synapse.
C. occurs only in endocrine cells.
D. has been found in plants but not animals.
E. mediates signaling to distant cells.
See Lecture 9. In paracrine signaling, a secretory cell that produces a secreting molecule (i.e., growth factors) will
release these molecules in the extracellular space through exocytosis. The signals will diffuse in that particular
region of the tissue and will only reach a few cells within that vicinity (local signaling).
25. From the perspective of the cell receiving the message, the three stages of cell signaling are:
A. the paracrine, local, and synaptic stages.
B. signal reception, signal transduction, and cellular response.
C. signal reception, nucleus disintegration, and new cell generation.
D. The alpha, beta, and gamma stages.
E. signal reception, cellular response, and cell division.
See Lecture 9.
26. One of the major categories of receptors in the plasma membrane reacts by forming dimmers, adding phosphate
groups, then activating relay proteins. Which type does this?
A. G protein-linked receptor
B. ligand-gated ion channels
C. steroid receptor
D. receptor tyrosine kinases
See Lecture 9.
27. Binding of a signaling molecule to which type of receptor leads directly to a change in distribution of Na+ on
opposite sides of the membrane?
A. receptor tyrosine kinase
B. G protein-coupled receptor
C. phosphorylated receptor tyrosine kinase dimer
D. Ligand-gated ion channel
See Lecture 9. These are especially important for communication between neurons (nerve cells). These ion
channels allow ions to flow down their concentration gradient.
Other things to consider for the Midterm II:
 Radish experiment
 Cell cycle inhibitor experiment (93stop)
 What prevents glucose from instantly combining with oxygen?