Cell bio chap18 M-phase cell division pt3

Sister chromatids are held together by protein complexes called __________.

cohesin

defective cohesion rings lead to major errors in chromosome segregation

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What initiates the M phase of cell division?

A) Cyclin D

B) M-Cdk complex

C) Separase

D) Cohesin rings

B

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True/False: The centrosome is responsible for the breakdown of the nuclear envelope during mitosis.

False (nuclear disassembly is the 1st event of pro metaphase and is not caused mitotic spindle of centrosome)

what are inerpolar microtubules

microtubules that interact with microtubules from other centrosome (those r said to be stable bcuz there’s no growing or shrinking)

when does centrosome replication occurs

A) In between G1 and S/G2

B) During S phase

C) In between S and G2

D) During G1

A

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attach the M phase stages

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

A) Prophase

B) Anaphase

C) Metaphase

D) Telophase

C

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The protein complex that assembles on each centromere during prophase is called __________.

Kinetochore (it is bi orientated meaning there’s 1 on each side of the centromere. It also serves as checkpoint to prevent chromosomal separation when chromatids unattached to kinetochore microtubules)

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True/False: Cohesin rings are broken by a protease called separase during anaphase.

True (the breaking of cohesion rings allows for kinetochore separation)

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Which structure serves as the microtubule-organizing center (MTOC)?

A) Centrosome

B) Kinetochore

C) Cleavage furrow

D) Contractile ring

A

True/False: The contractile ring disassembles after cytokinesis is complete.

True

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What happens to the nuclear envelope during telophase?

A) It breaks down completely for each set of chromosomes

B) It condenses into chromatin

C) It remains intact

D) It reassembles for each set of chromosomes

D

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What is the role of the Anaphase-Promoting Complex (APC)?

A) To degrade securin and inactivate separase

B) To degrade securin and activate separase

C) To condense chromosomes

D) To promote the separation of sister chromatids

B

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Define the centrosome cycle

It is the forming/degradation of asters

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The sliding filament mechanism during cytokinesis involves overlapping ______ and __________ filaments.

actin and myosin (happens after cell division)

If a mutation occurs that prevents separase from being activated, what would be the consequence for sister chromatids?

A) They would separate normally.

B) They would condense further.

C) They would be lost during cell division.

D) They would remain attached.

D

What is the typical range of kinetochore microtubules that attach to each sister chromatid during cell division in human cells?

A) 20 to 40

B) 10 to 20

C) 40 to 60

D) 60 to 80

A

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Which phase marks the transition from metaphase to anaphase?

A) Cohesin cleavage

B) Chromosome alignment

C) Nuclear envelope breakdown

D) Cytokinesis initiation

A

The __________ proteins enter through nuclear pores during telophase to help reform the nuclear envelope.

Nuclear (Nuclear envelope cycle is controlled by de/phosphorylation of nuclear pore proteins and lamins)

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Describe the role of cohesin rings in chromosome segregation during cell division.

Cohesin rings are protein complexes that hold sister chromatids together from the time they are replicated until they are separated during anaphase. if the sister chromatids were free to move around the nucleus it would be impossible to ensure that the chromosomes were accurately segregated. This is why cohesion is very important.

Explain how the Anaphase-Promoting Complex (APC) contributes to the separation of sister chromatids.

The Anaphase-Promoting Complex (APC) is an E3 ubiquitin ligase that triggers the transition from metaphase to anaphase by marking specific proteins for degradation. It degrades securin, a protein that inhibits separase. Once securin is degraded, separase is activated, which then cleaves cohesin rings, allowing sister chromatids to separate and be pulled toward opposite poles of the cell during anaphase.

The process by which the plasma membrane begins to cleave during cell division is known as __________.

Furrowing

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