BIOL 355 - 2025 Summer Name: Name is written on every page. Exam 3: Cell Cycle & Cell
Signaling Date:
Write your name on each page; points will be deducted for omitted names. Write concise, precise
sentences or lists, as appropriate. Do not exceed the space provided. Read all instructions carefully.
1. In this course, we have examined cell division in detail, in part to provide examples of cytoskeleton
dynamics, cell cycle regulation, and molecular pathways. (Total: 29 points)
A. Build a map of the interactions among the following components. Use arrows to represent activations
and blocking-arrows to represent inhibitions. Do not use any additional words on your map. Note: The
pathways may branch, converge, and feed back onto themselves. In other words, the pathways may
not be completely linear.
APC/C, BubR1, CAK, Cdc20, Cdc25, Cdk1, CENP-E, cohesin, M-phase entry/maintenance,
metaphase-to-anaphase transition, M-cyclin (i.e., cyclin B), Mad2, microtubule attachment/tension,
securin, separase, Wee1
Each of the following functional interactions is worth 1 point, for a total of 17 points.
microtubule attachment/tension ⊣ CENP-E → BubR1 → Mad2 ⊣ Cdc20 → APC/C ⊣ securin ⊣
separase ⊣ cohesin ⊣ metaphase-to-anaphase transition
CAK Cdc25
↓ ↓↑
… APC/C ⊣ M-cyclin (i.e., cyclin B) → Cdk1 → M-phase entry/maintenance
⊤⊥
Wee1
B. Based on the map, explain how a cell links transition into anaphase with exit from mitosis.
Activating APC/C (2 points) leads to degrading both cohesin (2 points) and M-cyclin (2 points),
linking the two processes.
C. Based on the map, what molecular, cellular, and organismal consequences would you predict for an
allele of Cdc25 that is overexpressed (and thus overactive)?
This allele could contribute to overactivation of Cdk1 (or M-Cdk) (2 points), cell division (2
points), and potentially cancer (2 points).
2. In this course, we have examined several signaling pathways in detail, in part to provide examples of
signaling principles. For each of the following components, identify one example. Be as specific as possible.
(Total: 34 points)
GPCR signaling pathway RTK signaling pathway
Page 1
, BIOL 355 - 2025 Summer Name: Name is written on every page. Exam 3: Cell Cycle & Cell
Signaling Date:
A. Component that catalyzes the adenylyl cyclase (2 points) n/a
formation of a nucleotide second
messenger
B. Component that amplifies the GPCR (2 points) Ras-GEF (Sos) or Ras (2 points)
signal non-enzymatically
C. Component that undergoes a Many answers are possible. Many answers are possible.
conformational change
D. Enzyme that modifies the phospholipase C-β (2 points) PI 3-kinase (2 points)
structure of PI(4,5)P2
E. GTPase Galpha or G protein (2 points) Ras (2 points)
F. Guanine nucleotide exchange GPCR (2 points) Ras-GEF (Sos) (2 points)
factor
G. Kinase that facilitates n/a PI 3-kinase or RTK (2 points)
recruitment
I. Kinase that participates in a PDK1 or AKT or mTOR (2
MAP kinase kinase kinase (Raf)
phosphorylation cascade points) or MAP kinase kinase (Mek) or
MAP kinase (Erk) (2 points)
J. Lipid that facilitates recruitment PI(4,5)P2 (2 points) PI(4,5)P2 (2 points)
or gives rise to second messenger
K. “Molecular switch” that has an Gα (2 points) Ras (2 points)
internal “molecular timer”
L. Phosphatase Phosphatases exist here, but we PTEN (2 points)
did not name them.
Page 2
Signaling Date:
Write your name on each page; points will be deducted for omitted names. Write concise, precise
sentences or lists, as appropriate. Do not exceed the space provided. Read all instructions carefully.
1. In this course, we have examined cell division in detail, in part to provide examples of cytoskeleton
dynamics, cell cycle regulation, and molecular pathways. (Total: 29 points)
A. Build a map of the interactions among the following components. Use arrows to represent activations
and blocking-arrows to represent inhibitions. Do not use any additional words on your map. Note: The
pathways may branch, converge, and feed back onto themselves. In other words, the pathways may
not be completely linear.
APC/C, BubR1, CAK, Cdc20, Cdc25, Cdk1, CENP-E, cohesin, M-phase entry/maintenance,
metaphase-to-anaphase transition, M-cyclin (i.e., cyclin B), Mad2, microtubule attachment/tension,
securin, separase, Wee1
Each of the following functional interactions is worth 1 point, for a total of 17 points.
microtubule attachment/tension ⊣ CENP-E → BubR1 → Mad2 ⊣ Cdc20 → APC/C ⊣ securin ⊣
separase ⊣ cohesin ⊣ metaphase-to-anaphase transition
CAK Cdc25
↓ ↓↑
… APC/C ⊣ M-cyclin (i.e., cyclin B) → Cdk1 → M-phase entry/maintenance
⊤⊥
Wee1
B. Based on the map, explain how a cell links transition into anaphase with exit from mitosis.
Activating APC/C (2 points) leads to degrading both cohesin (2 points) and M-cyclin (2 points),
linking the two processes.
C. Based on the map, what molecular, cellular, and organismal consequences would you predict for an
allele of Cdc25 that is overexpressed (and thus overactive)?
This allele could contribute to overactivation of Cdk1 (or M-Cdk) (2 points), cell division (2
points), and potentially cancer (2 points).
2. In this course, we have examined several signaling pathways in detail, in part to provide examples of
signaling principles. For each of the following components, identify one example. Be as specific as possible.
(Total: 34 points)
GPCR signaling pathway RTK signaling pathway
Page 1
, BIOL 355 - 2025 Summer Name: Name is written on every page. Exam 3: Cell Cycle & Cell
Signaling Date:
A. Component that catalyzes the adenylyl cyclase (2 points) n/a
formation of a nucleotide second
messenger
B. Component that amplifies the GPCR (2 points) Ras-GEF (Sos) or Ras (2 points)
signal non-enzymatically
C. Component that undergoes a Many answers are possible. Many answers are possible.
conformational change
D. Enzyme that modifies the phospholipase C-β (2 points) PI 3-kinase (2 points)
structure of PI(4,5)P2
E. GTPase Galpha or G protein (2 points) Ras (2 points)
F. Guanine nucleotide exchange GPCR (2 points) Ras-GEF (Sos) (2 points)
factor
G. Kinase that facilitates n/a PI 3-kinase or RTK (2 points)
recruitment
I. Kinase that participates in a PDK1 or AKT or mTOR (2
MAP kinase kinase kinase (Raf)
phosphorylation cascade points) or MAP kinase kinase (Mek) or
MAP kinase (Erk) (2 points)
J. Lipid that facilitates recruitment PI(4,5)P2 (2 points) PI(4,5)P2 (2 points)
or gives rise to second messenger
K. “Molecular switch” that has an Gα (2 points) Ras (2 points)
internal “molecular timer”
L. Phosphatase Phosphatases exist here, but we PTEN (2 points)
did not name them.
Page 2
