Cell-Cycle Control System and SCF Ubiquitin Ligase Quiz

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What is the first visible change of cytokinesis in an animal cell?

Division of the cell in two

Assembly of actin filaments

Formation of a contractile ring

Appearance of a cleavage furrow (correct)

Which structure is responsible for the division of an animal cell during cytokinesis?

Myosin II filaments

Contractile ring (correct)

Actin filaments

RhoA protein

What triggers the assembly and contraction of the contractile ring during cytokinesis?

Activation of RhoA by RhoGEF (correct)

Division of the cell in two

Assembly of actin filaments

Release of GDP by Myosin II

What is the function of RhoA in cytokinesis?

Control of contractile ring assembly Signup and view all the answers

Which protein is involved in the formation of the contractile ring in animal cells?

Actin filaments Signup and view all the answers

What is the role of a guanine nucleotide exchange factor (RhoGEF) during cytokinesis?

Stimulation of RhoA activation Signup and view all the answers

Which process occurs just beneath the plasma membrane during anaphase?

Assembly of the contractile ring Signup and view all the answers

What is the main structure underlying cytokinesis in an animal cell?

Contractile ring Signup and view all the answers

Where does the contractile ring assemble during cytokinesis?

Just beneath the plasma membrane Signup and view all the answers

What is the function of RhoA during cytokinesis?

Activating the contractile ring assembly and function Signup and view all the answers

Which protein is essential for the contraction of the contractile ring during animal cell cytokinesis?

Myosin II Signup and view all the answers

What triggers the formation of the cleavage furrow during cytokinesis in animal cells?

Contractile ring Signup and view all the answers

Which factor stimulates the release of GDP and binding of GTP to RhoA during cytokinesis?

RhoGEF Signup and view all the answers

What is the role of actin filaments in the contractile ring during cytokinesis?

Cell division contractility Signup and view all the answers

During which cell cycle phase does the contractile ring assemble in preparation for cell division?

Anaphase Signup and view all the answers

What is the role of cyclins in the activity of Cdks?

Binding to Cdks to activate them Signup and view all the answers

Which class of cyclins helps govern the activities of G1/S-cyclins in late G1?

G1-cyclins Signup and view all the answers

When do M-cyclin levels decrease?

Mid-mitosis Signup and view all the answers

Which type of cyclin stimulates entry into mitosis at the G2/M transition?

M-cyclins Signup and view all the answers

What happens to S-cyclin levels until mitosis begins?

They stay elevated until mitosis Signup and view all the answers

What is the role of securin destruction at the end of metaphase?

Leads to the separation of sister chromatids Signup and view all the answers

What is the consequence of APC/C targeting S- and Mcyclins for destruction?

Inactivation of Cdk activity in anaphase Signup and view all the answers

How does APC/C activation occur?

Phosphorylation of the APC/C Signup and view all the answers

What is the significance of M-Cdk promoting Cdc20–APC/C activity?

Creates a negative feedback loop for cyclin destruction Signup and view all the answers

What occurs when Cdk becomes inactivated in the cell cycle?

Activation of phosphatases for Cdk phosphorylation Signup and view all the answers

What is the role of the Anaphase-Promoting Complex/Cyclosome (APC/C) in late M phase events?

Facilitates the destruction of cyclins Signup and view all the answers

What is the function of Cdk-activating kinase (CAK) during M-Cdk activation?

Phosphorylates Cdk at an activating site Signup and view all the answers

What triggers the activation of the 'stockpile' of M-Cdk at the end of G2 phase?

Suppression of inhibitory phosphates by Cdc25 Signup and view all the answers

What is the role of protein phosphatase Cdc25 in M-Cdk activation?

Removes inhibitory phosphates from M-Cdk Signup and view all the answers

How does positive feedback loops contribute to M-Cdk activation during mitosis?

Inhibits its own inhibitor Wee1 and activates its activator Cdc25 Signup and view all the answers

What is the role of cyclin in the activation of Cdk?

Directs Cdk to specific target proteins Signup and view all the answers

Which type of phosphorylation inhibits the activity of a cyclin–Cdk complex?

Phosphorylation by Wee1 Signup and view all the answers

What structural change occurs in the Cdk protein upon binding with cyclin?

Loop moves away from the active site, partially activating the enzyme Signup and view all the answers

Which protein phosphorylates an amino acid near the entrance of the Cdk active site for full activation of the cyclin–Cdk complex?

CAK Signup and view all the answers

What effect does dephosphorylation by Cdc25 have on a cyclin–Cdk complex?

Increases Cdk activity Signup and view all the answers