Question 1

A loss-of-function mutation in which of the following would inhibit TGFβ signaling?

Accepted Answer

A) I-Smad 
B) R-Smad 
C) Ski 
D) SnoN 
E) all of the above 
A) I-Smad 
B) R-Smad 
C) Ski 
D) SnoN 
E) all of the above B

Question 2

Describe the role of adapter proteins in the activation of Ras by receptor tyrosine kinases.

Accepted Answer

Following dimerization and autophosphorylation of receptor tyrosine kinases,GRB2 and Sos proteins couple the receptor to the inactive Ras·GDP complex.Sos promotes dissociation of GDP from Ras,allowing GTP to bind.Sos acts as a guanine nucleotide exchange factor (GEF),which helps convert inactive Ras·GDP to active Ras·GTP.The Ras·GTP complex can then activate downstream effector molecules.

Question 3

Which of the following is cleaved by regulated intramembrane proteolysis (RIP)?

Accepted Answer

A) IB 
B) Notch 
C) TGFβ 
D) IB and TGFβ 
E) Notch and TGFβ 
A) IB 
B) Notch 
C) TGFβ 
D) IB and TGFβ 
E) Notch and TGFβ B

Question 4

Explain why,upon ligand binding,cell-surface receptors are often subjected to receptor-mediated endocytosis.

Accepted Answer

Removal of transmembrane receptors by re

Question 5

Latent TGFβ is converted to mature TGFβ by:

Accepted Answer

A) dephosphorylation. 
B) phosphorylation. 
C) proteolysis. 
D) translocation. 
E) none of the above 
A) dephosphorylation. 
B) phosphorylation. 
C) proteolysis. 
D) translocation. 
E) none of the above

Question 6

Predict the consequences of a temperature-sensitive mutation in which phosphorylation of the β-catenin protein is blocked.Above the permissive temperature:

Accepted Answer

A) β-catenin levels will increase and β-catenin will be constitutively active. 
B) β-catenin levels will increase and β-catenin will be inactive. 
C) β-catenin levels will decrease. 
D) β-catenin will remain constant but cells will be unresponsive to Wnt signaling. 
A) β-catenin levels will increase and β-catenin will be constitutively active. 
B) β-catenin levels will increase and β-catenin will be inactive. 
C) β-catenin levels will decrease. 
D) β-catenin will remain constant but cells will be unresponsive to Wnt signaling.

Question 7

Which protein stabilizes an intermediate in the Ras GTP hydrolysis reactions?

Accepted Answer

A) Sos 
B) GRB2 
C) RTK 
D) Raf 
A) Sos 
B) GRB2 
C) RTK 
D) Raf

Question 8

Ras is a(n):

Accepted Answer

A) adapter protein. 
B) guanine nucleotide exchange factor. 
C) kinase. 
D) protease. 
E) none of the above 
A) adapter protein. 
B) guanine nucleotide exchange factor. 
C) kinase. 
D) protease. 
E) none of the above

Question 9

Which of the following are enzyme pairs that catalyze opposite reactions?

Accepted Answer

A) MEK and MAP kinase 
B) NF-B and I-B 
C) PI-3 kinase and PTEN phosphatase 
D) JAKs and STATs 
E) none of the above 
A) MEK and MAP kinase 
B) NF-B and I-B 
C) PI-3 kinase and PTEN phosphatase 
D) JAKs and STATs 
E) none of the above

Question 10

Binding of erythropoietin to its extracellular receptor engages which of the following signaling pathways?

Accepted Answer

A) JAK/STAT 
B) Ras/MAP kinase 
C) PI-3 kinase 
D) all of the above 
E) none of the above 
A) JAK/STAT 
B) Ras/MAP kinase 
C) PI-3 kinase 
D) all of the above 
E) none of the above

Question 11

What feature allows TGFβ signaling molecules to be quickly mobilized?

Accepted Answer

TGFβ signaling molecules are s

Question 12

Which of the following is NOT true about the role of adapter proteins in the activation of Ras by receptor tyrosine kinases?

Accepted Answer

A) Following dimerization and autophosphorylation of receptor tyrosine kinases,GRB2 and Sos proteins couple to the receptor. 
B) GRB2 and Sos proteins couple the receptor to the inactive Ras·GDP complex. 
C) GRB2 interacts with Sos via its SH3 domain. 
D) Sos acts as a GAP,which helps convert Ras·GDP to active Ras·GTP. 
A) Following dimerization and autophosphorylation of receptor tyrosine kinases,GRB2 and Sos proteins couple to the receptor. 
B) GRB2 and Sos proteins couple the receptor to the inactive Ras·GDP complex. 
C) GRB2 interacts with Sos via its SH3 domain. 
D) Sos acts as a GAP,which helps convert Ras·GDP to active Ras·GTP.

Question 13

A gain-of-function mutation in which of the following would promote malignancy in cells whose proliferation is inhibited by TGFβ?

Accepted Answer

A) co-Smad 
B) I-Smad 
C) R-Smad 
D) all of the above 
E) none of the above 
A) co-Smad 
B) I-Smad 
C) R-Smad 
D) all of the above 
E) none of the above

Question 14

NF-B signaling is important in:

Accepted Answer

A) development. 
B) immunity. 
C) inflammation. 
D) immunity and inflammation. 
E) all of the above 
A) development. 
B) immunity. 
C) inflammation. 
D) immunity and inflammation. 
E) all of the above

Question 15

Many PTB-containing proteins act as docking sites for multiple proteins.If these proteins are involved in the RTK signal transduction pathway,they most likely:

Accepted Answer

A) contain GRB2 domains. 
B) are involved in autophosphorylation of the RTK. 
C) are phosphorylating the receptor and the docking protein. 
D) are adopting a different conformation (shape)to expand the pathways affected by ligand binding. 
A) contain GRB2 domains. 
B) are involved in autophosphorylation of the RTK. 
C) are phosphorylating the receptor and the docking protein. 
D) are adopting a different conformation (shape)to expand the pathways affected by ligand binding.

Question 16

Which of the following mechanisms is NOT used to terminate cytokine signaling and the JAK/STAT pathway?

Accepted Answer

A) transcription of SOCS proteins 
B) dephosphorylation of phosphotyrosine residues 
C) heterodimerization of cytokine receptors 
D) receptor internalization 
A) transcription of SOCS proteins 
B) dephosphorylation of phosphotyrosine residues 
C) heterodimerization of cytokine receptors 
D) receptor internalization

Question 17

How can multiple MAP kinase pathways be segregated when they share a common component,like a downstream kinase?

Accepted Answer

A) formation of pathway-specific complexes assembled on molecular scaffolds 
B) activation of different small G proteins 
C) differential activation of activation lip tyrosines 
D) phosphorylation of PTB-containing proteins 
A) formation of pathway-specific complexes assembled on molecular scaffolds 
B) activation of different small G proteins 
C) differential activation of activation lip tyrosines 
D) phosphorylation of PTB-containing proteins

Question 18

Compare and contrast the mechanisms by which SHP1 and SOCS proteins modulate erythropoietin signaling.

Accepted Answer

SHP1 and SOCS are both induced by negati

Question 19

By what mechanism does PI-3 phosphate promote activation of protein kinase B (PKB)?

Accepted Answer

A) recruiting PKB to the plasma membrane 
B) recruiting the activating kinase PDK1 to the plasma membrane 
C) releasing inhibition of the catalytic site by the PH domain 
D) the first and second answers are correct 
E) all of the above 
A) recruiting PKB to the plasma membrane 
B) recruiting the activating kinase PDK1 to the plasma membrane 
C) releasing inhibition of the catalytic site by the PH domain 
D) the first and second answers are correct 
E) all of the above

Question 20

Serum response factor (SRF)is phosphorylated by:

Accepted Answer

A) MEK. 
B) MAP kinase. 
C) p90ᴿˢᴷ. 
D) Raf. 
E) Ras. 
A) MEK. 
B) MAP kinase. 
C) p90ᴿˢᴷ. 
D) Raf. 
E) Ras.

Exam 15: Signaling Pathways That Control Gene Activity

A loss-of-function mutation in which of the following would inhibit TGFβ signaling?

Describe the role of adapter proteins in the activation of Ras by receptor tyrosine kinases.

Which of the following is cleaved by regulated intramembrane proteolysis (RIP)?

Explain why,upon ligand binding,cell-surface receptors are often subjected to receptor-mediated endocytosis.

Latent TGFβ is converted to mature TGFβ by:

Predict the consequences of a temperature-sensitive mutation in which phosphorylation of the β-catenin protein is blocked.Above the permissive temperature:

Which protein stabilizes an intermediate in the Ras GTP hydrolysis reactions?

Ras is a(n):

Which of the following are enzyme pairs that catalyze opposite reactions?

Binding of erythropoietin to its extracellular receptor engages which of the following signaling pathways?

What feature allows TGFβ signaling molecules to be quickly mobilized?

Which of the following is NOT true about the role of adapter proteins in the activation of Ras by receptor tyrosine kinases?

A gain-of-function mutation in which of the following would promote malignancy in cells whose proliferation is inhibited by TGFβ?

NF-B signaling is important in:

Many PTB-containing proteins act as docking sites for multiple proteins.If these proteins are involved in the RTK signal transduction pathway,they most likely:

Which of the following mechanisms is NOT used to terminate cytokine signaling and the JAK/STAT pathway?

How can multiple MAP kinase pathways be segregated when they share a common component,like a downstream kinase?

Compare and contrast the mechanisms by which SHP1 and SOCS proteins modulate erythropoietin signaling.

By what mechanism does PI-3 phosphate promote activation of protein kinase B (PKB)?

Serum response factor (SRF)is phosphorylated by:

Chemical Foundations

Molecular Genetic Techniques

Protein Structure and Function

Culturing and Visualizing Cells

Fundamental Molecular Genetic Mechanisms

Bio-membrane Structure

Genes Genomics and Chromosomes

Transcriptional Control of Gene Expression

Post-Transcriptional Gene Control

Transmembrane Transport of Ions and Small Molecules

Cellular Energetics

Moving Proteins Into Membranes and Organelles

Vesicular Traffic, Secretion, and Endocytosis

Signal Transduction and G-Protein Coupled Receptors

Cell Organization and Movement I: Microfilaments

Cell Organization and Movement II: Microtubules and Intermediate Filaments

Regulating the Eukaryotic Cell Cycle

Integrating Cells Into Tissues

Cell Birth, Lineage, and Death

Nerve Cells

Immunology

Cancer

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