MCAT Biological and Biochemical Foundations of Living Systems Quiz: 2c Mitosis Chromosome Dynamics

What this quiz covers

This quiz focuses on 2c Mitosis Chromosome Dynamics, giving you a quick way to practice the rules, question types, and explanations that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Stabilizing kinetochore microtubules can delay satisfaction of the SAC by reducing error-correction and the acquisition of stable bi-orientation needed for metaphase alignment. (correct answer)
2. The treatment primarily blocks sister chromatid separation by preventing cohesin cleavage, so chromosomes remain aligned but cannot enter anaphase.
3. The treatment accelerates anaphase by increasing poleward microtubule flux, pulling chromosomes away from the metaphase plate earlier than normal.
4. The treatment causes homologous chromosomes to fail to synapse, leading to persistent SAC signaling and misalignment.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on how reduced microtubule dynamics affects chromosome alignment and spindle assembly checkpoint (SAC) satisfaction. Choice A is correct because it accurately describes how stabilizing kinetochore microtubules prevents the error-correction mechanisms needed for proper bi-orientation, as supported by the data showing mispositioned chromosomes with persistent SAC proteins. Choice B is incorrect because it describes a separase/cohesin issue, but the data shows alignment problems before anaphase, not a block after metaphase alignment. When analyzing mitosis, ensure that treatments affecting microtubule dynamics are understood to impact attachment correction and bi-orientation establishment, which are prerequisites for SAC satisfaction.

Question 2

1. Reformation of the nuclear envelope around decondensing chromosomes at each pole.
2. Separation of sister chromatids due to cohesin cleavage and movement of chromatids toward the spindle poles.
3. Stable bi-oriented attachment of sister kinetochores to microtubules from opposite poles with sustained tension across the centromere. (correct answer)
4. Pairing of homologous chromosomes into bivalents to promote reductional division.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on how partial microtubule suppression affects metaphase chromosome alignment. Choice C is correct because it describes stable bi-oriented attachment with tension, which requires robust microtubule dynamics and would be disrupted by nocodazole treatment, as supported by the data showing alignment failure and SAC persistence. Choice B is incorrect because it describes anaphase events, while the question asks about metaphase, and the cells are arrested before anaphase. When analyzing mitosis, understand that proper metaphase requires stable bi-oriented attachments generating tension, which depends on dynamic microtubules for error correction and attachment maturation.

Question 3

1. Separase activity is required for DNA replication origin firing; without it, cells enter mitosis with unreplicated chromosomes that cannot align.
2. Separase activity is required for kinetochore-microtubule attachment; without it, chromosomes cannot congress and remain near spindle poles.
3. Separase activity is required for centrosome separation in prophase; without it, cells form monopolar spindles and never reach metaphase.
4. Separase activity is required for cohesin cleavage at anaphase onset; without separase activation, sister chromatids remain paired despite normal metaphase alignment. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on separase function in triggering sister chromatid separation at anaphase onset. Choice D is correct because it accurately describes how separase cleaves cohesin to allow sister chromatid separation, as supported by the data showing normal metaphase but failure to separate chromatids despite SAC satisfaction. Choice C is incorrect because it describes a prophase centrosome function, while the data shows normal spindle formation and metaphase plate assembly. When analyzing mitosis, remember that separase activation is the final trigger for anaphase, cleaving cohesin rings that hold sister chromatids together.

Question 4

1. Topoisomerase II is required for homolog recombination; inhibition prevents crossing over and causes anaphase bridges in meiosis II.
2. Topoisomerase II is required to attach microtubules to kinetochores; inhibition prevents metaphase alignment and activates the SAC.
3. Topoisomerase II is required to degrade cyclin B; inhibition prevents mitotic entry and keeps cells in G1.
4. Topoisomerase II is required to resolve residual catenation between sister chromatids; inhibition can cause anaphase bridges despite normal alignment. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on topoisomerase II function during sister chromatid separation. Choice D is correct because it accurately describes how topoisomerase II resolves DNA catenations between sister chromatids that persist after replication, as supported by the data showing normal alignment but DNA bridges during separation. Choice B is incorrect because it describes a kinetochore attachment function, while the data shows normal metaphase alignment indicating proper attachments. When analyzing mitosis, recognize that topoisomerase II is essential for complete chromatid disjunction by resolving topological links between sister DNAs.

Question 5

1. Cortical pulling on astral microtubules contributes mainly to anaphase B spindle pole separation, whereas anaphase A can proceed via kinetochore microtubule shortening. (correct answer)
2. Cortical pulling forces are required for metaphase chromosome condensation, explaining the two-phase anaphase movement.
3. Astral microtubules primarily attach to kinetochores to pull chromatids toward the metaphase plate during anaphase.
4. Reduced spindle pole separation indicates failure of homologous chromosomes to disjoin during meiosis I.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on spindle pole separation during anaphase B, influenced by disruption of cortical pulling on astral microtubules. Choice A is correct because it accurately describes cortical pulling's role in anaphase B while anaphase A proceeds via shortening, as supported by the data showing reduced separation but maintained initial movement. Choice C is incorrect because it describes astral attachment to kinetochores, a common error if astral functions are misplaced. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 6

1. Poleward chromatid movement in anaphase A depends on intact kinetochore microtubules, whereas anaphase B can proceed via spindle elongation mechanisms. (correct answer)
2. Kinetochore microtubules are primarily required to re-form the nuclear envelope during telophase.
3. Chromatids move away from poles during anaphase A because kinetochore microtubules polymerize at kinetochores.
4. Anaphase A requires homologous chromosome pairing, explaining the side-specific slowing after k-fiber inactivation.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on chromatid movement during anaphase A and B, influenced by kinetochore microtubule inactivation. Choice A is correct because it accurately describes the role of intact kinetochore microtubules in anaphase A poleward movement while anaphase B proceeds via elongation, as supported by the data showing side-specific slowing. Choice C is incorrect because it describes microtubule polymerization pushing chromatids away from poles, a common error if depolymerization-driven movement is misunderstood. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 7

1. Weakening the SAC allows anaphase onset before all kinetochores achieve proper bipolar attachment, increasing missegregation and micronuclei formation. (correct answer)
2. Weakening the SAC prevents cytokinesis by blocking actin ring formation, causing multinucleated cells.
3. Weakening the SAC causes sister chromatids to rejoin during anaphase, producing lagging chromosomes.
4. Weakening the SAC increases crossing over between homologs, generating micronuclei during meiosis I.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on spindle assembly checkpoint function during metaphase, influenced by SAC weakening. Choice A is correct because it accurately describes how weakened SAC allows premature anaphase with missegregation, as supported by the data showing lagging chromosomes and micronuclei. Choice B is incorrect because it describes SAC's role in cytokinesis via actin, a common error if checkpoint functions are confused with contractile ring assembly. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 8

1. Stable end-on attachments occur only after cytokinesis, so low marker levels indicate failed abscission.
2. Aurora B activation promotes cohesin cleavage, causing premature anaphase and reduced marker accumulation.
3. Aurora B activation primarily blocks centrosome duplication, so fewer microtubules form and the marker cannot accumulate.
4. Increased Aurora B activity can destabilize kinetochore-microtubule attachments, impairing the transition to stable end-on binding needed for alignment. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on attachment stability during prometaphase to metaphase, influenced by Aurora B activation. Choice D is correct because it accurately describes how increased activity destabilizes attachments, as supported by the data showing low marker and failed alignment. Choice B is incorrect because it describes promotion of cohesin cleavage, a common error if Aurora B's corrective role is confused with anaphase initiation. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 9

1. CDK1 activity triggers homologous chromosome pairing at the metaphase plate, explaining spindle defects in somatic cells.
2. CDK1 activity is required only after cytokinesis to initiate DNA replication, so reduced activity should not affect mitosis.
3. CDK1 activity directly forms kinetochore microtubules by acting as a structural component of tubulin.
4. CDK1 activity promotes coordinated mitotic entry events such as chromosome condensation and spindle assembly; reduced activity delays and destabilizes early mitosis. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on the role of CDK1 in coordinating early mitotic events like chromosome condensation and spindle assembly during prophase and prometaphase, influenced by its kinase activity. Choice D is correct because it accurately describes the role of CDK1 in promoting these coordinated events, as supported by the observed delays and defects with reduced activity, while later alignment occurs once the spindle forms. Choice B is incorrect because it misattributes CDK1's role to post-mitotic DNA replication, a common error if confusing CDK1 with other cyclins involved in S phase. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 10

1. Dynamic microtubule turnover is important for error correction and stable biorientation; reducing dynamics promotes persistent incorrect attachments and SAC delay. (correct answer)
2. Microtubule stabilization primarily blocks DNA synthesis, indirectly delaying anaphase onset.
3. Stable biorientation requires homologous chromosomes to pair at the metaphase plate, so stabilization prevents synapsis.
4. Reducing microtubule dynamics should accelerate anaphase by increasing separase activity at kinetochores.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on biorientation during metaphase, influenced by reduced microtubule dynamics from stabilization. Choice A is correct because it accurately describes the importance of dynamics for error correction and stable attachments, as supported by the data showing delayed anaphase and missegregation. Choice D is incorrect because it suggests acceleration of anaphase, a common error if stabilization's inhibitory effects are misunderstood. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 11

1. APC/C activity initiates synapsis and crossing over between homologous chromosomes at metaphase.
2. APC/C activity is required for spindle microtubule nucleation at centrosomes during prophase.
3. APC/C activity directly polymerizes actin to form the contractile ring during cytokinesis.
4. APC/C activity promotes the metaphase-to-anaphase transition by targeting key proteins for degradation, enabling chromatid separation and mitotic exit. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on the metaphase-to-anaphase transition, influenced by APC/C inhibition maintaining cyclin B and cohesion. Choice D is correct because it accurately describes APC/C's role in promoting the transition via degradation, as supported by the data showing metaphase accumulation and rapid progression upon washout. Choice B is incorrect because it describes prophase nucleation, a common error if APC/C timing is misplaced. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 12

1. Checkpoint satisfaction depends not only on attachment but also on tension generated by proper biorientation, which is reduced in the mutant. (correct answer)
2. Low inter-kinetochore distance indicates that sister chromatids have already separated, so SAC proteins persist to prevent telophase.
3. SAC proteins persist because DNA replication is incomplete, and tension is generated only during S phase.
4. The mutant increases homologous pairing, so SAC proteins remain until meiosis I is completed.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on spindle assembly checkpoint satisfaction during metaphase, influenced by mutant kinetochore protein reducing tension. Choice A is correct because it accurately describes the dependence on tension for checkpoint satisfaction, as supported by the data showing low distance and persistent SAC proteins. Choice B is incorrect because it suggests chromatids have separated, a common error if low tension is misinterpreted as separation. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 13

1. Kinesin-13–mediated microtubule depolymerization contributes to anaphase A poleward movement by shortening kinetochore microtubules. (correct answer)
2. Kinesin-13 inhibition accelerates metaphase alignment by increasing microtubule growth at centrosomes.
3. Anaphase requires microtubule polymerization at kinetochores to push chromatids toward the spindle midzone.
4. Kinesin-13 is required for homologous chromosome segregation, explaining the reduced chromatid velocity.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on chromatid movement during anaphase A, influenced by kinesin-13 inhibition at kinetochores. Choice A is correct because it accurately describes kinesin-13's role in microtubule depolymerization for poleward movement, as supported by the data showing reduced velocity and increased microtubule mass. Choice C is incorrect because it describes polymerization pushing chromatids to the midzone, a common error if depolymerization mechanisms are reversed. When analyzing mitosis, ensure the phase-specific activities are matched with correct events and components; consider regulatory influences at each stage.

Question 14

1. Stabilizing microtubules can reduce correction of improper kinetochore attachments, delaying congression to the metaphase plate. (correct answer)
2. Stabilizing microtubules directly triggers separase activation, causing premature sister chromatid separation during prometaphase.
3. Stabilizing microtubules prevents DNA replication, leading to unreplicated chromosomes that cannot align at metaphase.
4. Stabilizing microtubules forces homologous chromosomes to pair, creating bivalents that stall at the metaphase plate.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on microtubule dynamics during prometaphase, where dynamic instability allows error correction through attachment-detachment cycles. Choice A is correct because it accurately describes how stabilizing microtubules reduces the ability to correct improper attachments, causing chromosomes to remain near one pole rather than congressing to the metaphase plate. Choice B is incorrect because stabilizing microtubules does not directly trigger separase activation - this requires APC/C activation and checkpoint satisfaction. When analyzing mitosis, ensure that microtubule dynamics are understood as essential for error correction; reduced dynamics impair the search-and-capture mechanism needed for proper bi-orientation.

Question 15

1. Kinesin-5 is required for cleavage furrow ingression, so inhibiting it slows cytokinesis rather than anaphase movement.
2. Kinesin-5 primarily contributes to anaphase B spindle pole separation, while chromatid-to-pole movement can still occur via other mechanisms. (correct answer)
3. Kinesin-5 is the enzyme that cleaves cohesin, so inhibiting it prevents sister chromatid separation.
4. Kinesin-5 inhibition blocks synapsis of homologous chromosomes, reducing pole separation during meiosis I.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on anaphase chromosome movement, which consists of anaphase A (chromatid-to-pole movement) and anaphase B (spindle pole separation). Choice B is correct because it accurately describes that kinesin-5 primarily drives spindle pole separation in anaphase B, while chromatid movement to poles can occur through kinetochore microtubule depolymerization and other mechanisms. Choice C is incorrect because kinesin-5 is a motor protein, not the separase enzyme that cleaves cohesin. When analyzing mitosis, distinguish between anaphase A and B mechanisms; multiple motors and forces contribute to different aspects of chromosome segregation.

Question 16

1. Sustained CDK activity is required to maintain the mitotic state; lowering CDK activity can promote exit-like events even without anaphase. (correct answer)
2. CDK activity is required to initiate DNA synthesis, so inhibiting CDK in mitosis forces a return to S phase.
3. CDK inhibition prevents kinetochore assembly, which normally occurs only after cytokinesis is complete.
4. CDK activity is required for homolog pairing, so inhibition blocks tetrad formation and prevents metaphase I alignment.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on CDK activity's role in maintaining the mitotic state, where high CDK-cyclin B activity keeps cells in mitosis. Choice A is correct because it accurately describes how lowering CDK activity can trigger mitotic exit events like nuclear envelope reformation and chromatin decondensation, even without proper anaphase. Choice B is incorrect because CDK inhibition in mitosis does not force a return to S phase - cells exit mitosis toward G1. When analyzing mitosis, remember that sustained CDK activity maintains mitotic features; its decline drives exit regardless of whether anaphase has occurred properly.

Question 17

1. Low kinetochore tension reflects pairing of homologous chromosomes, which is required for accurate mitotic segregation.
2. Low kinetochore tension indicates that chromosomes are still unreplicated, so sister chromatids cannot separate in anaphase.
3. Low kinetochore tension is expected only after telophase begins, when chromosomes decondense and the spindle disassembles.
4. Apparent alignment alone is insufficient; stable bi-orientation with tension helps ensure correct segregation at anaphase. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on the relationship between kinetochore tension and proper bi-orientation, where tension indicates correct attachment to opposite spindle poles. Choice D is correct because it accurately describes how apparent alignment without proper tension indicates unstable or incorrect attachments that can lead to missegregation. Choice B is incorrect because low tension does not indicate unreplicated chromosomes - sister chromatids exist but lack proper opposing forces. When analyzing mitosis, recognize that both alignment and tension are required; tension serves as a quality control mechanism ensuring chromosomes are properly bi-oriented before anaphase.

Question 18

1. Pairing of homologous chromosomes into bivalents, enabling their alignment on the metaphase plate.
2. Reformation of the nuclear envelope around decondensing chromosomes, producing two daughter nuclei.
3. Separation of sister chromatids by cohesin cleavage, initiating their movement toward the metaphase plate.
4. Bioriented attachment of sister kinetochores to microtubules from opposite spindle poles, generating tension across sister chromatids. (correct answer)

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on how monopolar spindles prevent biorientation, which requires attachment of sister kinetochores to opposite spindle poles. Choice D is correct because it accurately describes the bioriented attachment that occurs during metaphase in normal bipolar spindles but cannot occur in monopolar spindles where all microtubules emanate from a single pole, as supported by the data showing radial chromosome arrangement and rare anaphase onset. Choice B is incorrect because nuclear envelope reformation occurs during telophase, not metaphase, and is not directly related to spindle bipolarity. When analyzing mitosis, ensure that spindle geometry requirements are matched with specific mitotic events; consider that biorientation requires two spindle poles.

Question 19

1. It promotes congression by generating forces that move mono-oriented chromosomes toward the spindle equator along microtubules. (correct answer)
2. It cleaves cohesin at anaphase onset to allow sister chromatids to separate.
3. It initiates nuclear envelope breakdown to permit spindle microtubules to contact chromosomes.
4. It separates homologous chromosomes by dissolving chiasmata during meiosis I.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on a plus-end-directed kinetochore motor and its role in chromosome congression. Choice A is correct because it accurately describes how plus-end-directed motors at kinetochores generate forces for congression of mono-oriented chromosomes toward the metaphase plate, as supported by the data showing chromosomes stuck near poles with persistent SAC signaling. Choice B is incorrect because it describes separase function, not a motor protein function, and the issue is with alignment, not separation. When analyzing mitosis, understand that kinetochore motors provide directional forces essential for chromosome congression to the spindle equator.

Question 20

1. The inhibited motor most likely contributes to anaphase A by depolymerizing kinetochore microtubules to pull chromatids toward the equator.
2. The inhibited motor most likely contributes to anaphase B by promoting antiparallel microtubule sliding that separates spindle poles. (correct answer)
3. The inhibited motor most likely triggers prophase by initiating centrosome duplication, indirectly shortening anaphase.
4. The inhibited motor most likely prevents crossing over between homologs, reducing pole separation and blocking cytokinesis.

Explanation: This question assesses understanding of mitosis and chromosome dynamics within the cell cycle. Mitosis involves precise chromosome alignment and segregation, regulated by specific proteins and checkpoints. In this scenario, the focus is on a kinesin motor at the spindle midzone and its role in anaphase dynamics. Choice B is correct because it accurately describes the role of midzone kinesins in anaphase B (pole separation through antiparallel microtubule sliding), as supported by the data showing normal chromatid-to-pole movement but reduced pole separation. Choice A is incorrect because it confuses anaphase A (chromatid-to-pole movement) with the midzone motor's actual function, and the data shows normal initial chromatid movement. When analyzing mitosis, distinguish between anaphase A (kinetochore-driven) and anaphase B (midzone-driven) mechanisms to correctly interpret motor protein functions.