$$\text{Cdk activity} \propto \text{Cyclin concentration}$$

$$\text{S-Cdk} + \text{ORC/Cdc6} \rightarrow \text{Phosphorylated ORC/Cdc6}$$

Question 1

Which protein complex is responsible for holding sister chromatids together until anaphase during mitosis?

Accepted Answer

Cohesin

Question 2

What is the primary function of the anaphase-promoting complex/cyclosome (APC/C) during mitosis?

Accepted Answer

Promotes destruction of cohesins to trigger sister chromatid separation

Question 3

During the cell cycle, which event ensures that DNA replication occurs only once per cycle?

Accepted Answer

Phosphorylation of ORC and Cdc6 by S-Cdk

Question 4

Which stage of mitosis is characterized by the alignment of chromosomes at the equator of the spindle?

Accepted Answer

Metaphase

Question 5

What is the role of the protein phosphatase PP2A in cell cycle regulation?

Accepted Answer

Reverses the effects of Cdks by dephosphorylation

Question 6

Which equation best represents the relationship between cyclin concentration and Cdk activity during the cell cycle?

Accepted Answer

$$	ext{Cdk activity} \propto 	ext{Cyclin concentration}$$

Question 7

Which Nobel Prize-winning discovery is directly related to the marking of proteins for degradation in the cell cycle?

Accepted Answer

Ubiquitin-mediated protein degradation

Question 8

What is the function of the pre-replicative complex (preRC) in chromosome duplication?

Accepted Answer

Licenses replication origins for DNA replication

Question 9

Which protein is a key regulator that promotes the formation of the preRC at replication origins?

Accepted Answer

Cdc6

Question 10

During which phase of the cell cycle does the assembly of new Mcm helicases at replication origins occur?

Accepted Answer

G1 phase

Question 11

Which of the following best describes the positive feedback loop in M-Cdk activation?

Accepted Answer

M-Cdk phosphorylates Cdc25, which further activates M-Cdk

Question 12

What is the main function of condensin during mitosis?

Accepted Answer

Promoting chromosome condensation and loop formation

Question 13

Which stage of mitosis involves the breakdown of the nuclear envelope and attachment of chromosomes to spindle microtubules?

Accepted Answer

Prometaphase

Question 14

Which process is regulated by the phosphorylation and dephosphorylation of Cdk substrates?

Accepted Answer

Cell cycle progression

Question 15

In cytokinesis of animal cells, which cytoskeletal components form the contractile ring?

Accepted Answer

Actin and myosin II

Question 16

Which equation describes the effect of S-Cdk on ORC and Cdc6 during the cell cycle?

Accepted Answer

$$	ext{S-Cdk} + 	ext{ORC/Cdc6} ightarrow 	ext{Phosphorylated ORC/Cdc6}$$

Question 17

Which Nobel Prize-winning method is used for the diagnosis of sickle cell anemia by amplifying beta-globin genomic sequences?

Accepted Answer

Polymerase chain reaction (PCR)

Question 18

What is the effect of APC/C activation on the cell cycle?

Accepted Answer

Triggers sister chromatid separation and cyclin degradation

Question 19

Which protein is responsible for removing the inhibitory phosphate group from M-Cdk, thus activating it?

Accepted Answer

Cdc25

Question 20

Which stage of mitosis is directly followed by cytokinesis?

Accepted Answer

Telophase

24: Cell Cycle Control and Mitosis: Key Mechanisms and Regulatory Proteins

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