Cell Cycle, Mitosis, and Cytokinesis

Flashcards testing concepts of the cell cycle, phases of interphase, stages of mitosis, and differences in cytokinesis and cellular structures between plants and animals.

According to cell theory and general cell biology, what are the smallest units that exhibit all emergent properties of life?

Cells are the smallest units that exhibit all emergent properties of life, and all cells come from preexisting cells.

What are the two notable exceptions to the routine and accurate execution of the cell cycle?

Cancer (uncontrolled growth and division) and apoptosis (programmed cell death).

What proportion of the cell cycle does interphase comprise in an actively dividing human skin cell?

Interphase can encompass $50\%$ to $90\%$ of the cell cycle in actively dividing cells.

In what state or phase do non-dividing cells, such as most brain cells, typically exist?

They may exist indefinitely in interphase or in a phase called $G_0$, with no probability of mitosis or cell division.

What major events occur during the $G_1$ phase of interphase?

The cell grows in size and accumulates enzymes required for DNA replication.

What occurs during the $S$ phase of interphase?

Exact replication of chromosomes (DNA) is synthesized so that each daughter cell will be genetically identical to the parent cell.

What cellular activities take place during the $G_2$ phase of interphase?

The cell generates new organelles, accumulates nutrients, and prepares for cell division.

How do animal somatic cells differ from gametes in terms of ploidy and chromosome set count?

Somatic cells (body cells) are diploid ($2n$) with paired chromosomes inherited from each parent, whereas gametes (eggs and sperm) are haploid ($n$) with only one copy of each chromosome.

What sequence of distinct stages makes up the continuous process of mitosis?

Prophase, metaphase, anaphase, and telophase.

What key cellular changes occur during prophase?

Sister chromatids condense into coils visible under a light microscope, the nuclear envelope disintegrates, and a spindle apparatus forms from microtubules, attaching to centromeres via kinetochore fibers.

What diagnostic technique uses the visible condensed sister chromatids present during prophase?

Karyotyping.

What events characterize metaphase and signal its conclusion?

Attached sister chromatids migrate to the cell's imaginary equator (metaphase plate) where spindle fibers pull on them until they break apart at the centromere, marking the end of metaphase.

What defines anaphase, and what status do sister chromatids gain once separated?

Anaphase is the movement of separated chromatids toward opposite poles away from the metaphase plate; upon separation, they take on official chromosome status. It is usually the shortest phase in mitosis.

What main structural changes take place during telophase?

The spindle apparatus breaks down, a nuclear envelope re-forms around the chromosomes, and the chromosomes uncoil, decondense, and return to their interphase state.

How does cytokinesis differ between animal cells and plant cells?

In animal cells, a cleavage furrow forms during cytokinesis (first appearing in telophase) and pinches inward. In plant cells, a cell plate forms extending from the center of the metaphase plate outward across the cell.

What structural feature anchors the spindle poles in animal cells during mitosis that is absent in plant cells?

Animal cells have specialized microtubule structures called centrioles in their centrosomes, while plant cells undergo mitosis without centrioles at the poles.