Cell Cycle and Mitosis

These flashcards cover key concepts and details about the cell cycle and mitosis, including phases, regulatory proteins, checkpoints, and processes involved in cellular reproduction.

What are the four phases of the cell cycle?

G1, S, G2, and M phases.

What do cleavage divisions lack in terms of the cell cycle?

Cleavage divisions have no G1 and G2 phases.

What is the role of checkpoints in the cell cycle control system?

Checkpoints ensure that each step is completed properly before moving to the next phase.

What activates cyclin-dependent protein kinases (Cdks)?

Activation relies on specific protein cyclins binding to Cdks.

What event triggers the cell cycle?

The cell cycle is triggered by the progression of cellular events and signals.

What is p53 and its role in the cell cycle?

p53 is a transcriptional activator that triggers the expression of p21, a Cdk inhibitor, in response to DNA damage.

How does S-Cdk regulate DNA replication?

S-Cdk ensures that DNA replication occurs only once per cycle by regulating the disassembly of the pre-replicative complex.

What are cohesins and condensins?

Cohesins hold sister chromatids together, while condensins compact chromosomes during mitosis.

What is the function of the anaphase-promoting complex (APC)?

APC is a ubiquitin ligase that promotes the degradation of mitotic cyclins and securin, allowing sister chromatids to separate.

How do microtubules aid in mitosis?

Microtubules form the mitotic spindle which helps segregate sister chromatids during anaphase.

What happens during apoptosis concerning DNA damage?

Cells are driven to death via apoptosis if damage to DNA is detected by the p53 pathway.

What are the two types of checkpoint signals in the cell cycle?

Positive signals that promote progression and negative signals that halt the cycle due to errors.

Where does centrosome duplication begin?

Centrosome duplication begins at the start of S phase.

What happens to nuclear lamins during mitosis?

Nuclear lamins are phosphorylated, leading to the breakdown of the nuclear envelope.

What is the function of G1-Cdk activity?

G1-Cdk activity promotes the transcription of genes required for entry into the S phase.

What role do astral microtubules play during anaphase?

Astral microtubules help anchor the centrosome and facilitate the separation of the spindle poles.

What occurs if signals are unfavorable during the cell cycle?

Cells may be directed to undergo apoptosis if signals indicate damage or improper conditions.

What is the role of checkpoints in the cell cycle?

Checkpoints are regulatory mechanisms that ensure the proper completion of each phase of the cell cycle before progressing to the next phase.

What happens during prophase?

In prophase, chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and the spindle apparatus begins to form.

What occurs during metaphase?

During metaphase, chromosomes align at the cell's equatorial plate, and spindle fibers attach to their centromeres.

Define anaphase.

Anaphase is the stage where sister chromatids are pulled apart and moved to opposite poles of the cell.

What is telophase?

Telophase is the final stage of mitosis where the chromosomes de-condense, the nuclear envelopes re-form, and the cell prepares for division.

What is the significance of the G0 phase?

The G0 phase is a resting state where cells exit the cycle and cease division, often indefinitely, until conditions favor re-entry.

How do cancer cells relate to the cell cycle?

Cancer cells often bypass cell cycle checkpoints, leading to uncontrolled division and growth.

What is the difference between asexual and sexual reproduction in terms of the cell cycle?

Asexual reproduction typically involves mitosis, while sexual reproduction involves meiosis, which includes two rounds of cell division and results in genetically diverse gametes.

What is cancer's effect on the cell cycle?

Cancer can disrupt normal checkpoints, leading to uncontrolled and rapid cell division.

What are oncogenes?

Oncogenes are mutated genes that promote the cell cycle and can lead to cancerous growth.

What are tumor suppressor genes?

Tumor suppressor genes are responsible for inhibiting cell division and repairing DNA; mutations can prevent their function, leading to cancer.

Explain the purpose of the spindle apparatus.

The spindle apparatus is responsible for the movement of chromosomes during mitosis.

What occurs during cytokinesis in animal cells?

In animal cells, cytokinesis occurs through a cleavage furrow that pinches the cell in two.

Describe cytokinesis in plant cells.

In plant cells, cytokinesis occurs through the formation of a cell plate, which develops into a new cell wall.

What is a sister chromatid?

A sister chromatid is one of the two identical halves of a duplicated chromosome, which are joined at the centromere.

Define the M phase of the cell cycle.

The M phase is the phase of the cell cycle where mitosis and cytokinesis occur, resulting in cell division.

What are the main phases of mitosis?

The main phases of mitosis include prophase, metaphase, anaphase, and telophase.

What occurs during prophase I of meiosis?

In prophase I of meiosis, homologous chromosomes pair up and exchange genetic material through crossing-over.

What is the significance of crossing-over?

Crossing-over increases genetic diversity by exchanging segments between homologous chromosomes during meiosis.

What is the difference between meiosis and mitosis?

Meiosis results in four genetically diverse gametes, while mitosis produces two identical daughter cells.

Explain the role of the centrosome during cell division.

The centrosome organizes the microtubules of the spindle apparatus and helps to pull chromosomes apart during mitosis.

What are the consequences of errors in DNA replication?

Errors in DNA replication can lead to mutations, which may cause malfunctioning proteins or contribute to cancer.

How do growth factors influence the cell cycle?

Growth factors are signals that promote cell division and can trigger cells to move from G0 to the G1 phase.

What is apoptosis, and how does it relate to the cell cycle?

Apoptosis is programmed cell death that eliminates damaged or unnecessary cells, helping maintain tissue homeostasis and prevent cancer.