Cell Division — Practice Quiz
A Biology cheat sheet for Cell Division — every key formula with its symbols defined — plus a medium-level practice quiz to test recall.
Formulas & key concepts
<img src='cell division.png' style='width:100%; max-width:500px; display:block; margin: 10px auto;' alt='Cell Division Diagram'>
<b>Surface Area to Volume Ratio</b>: As a cell grows, volume increases faster than surface area, making nutrient exchange inefficient. DNA overload also limits size.
<b>Asexual</b>: Single parent, genetically identical offspring (e.g., Binary Fission in bacteria). Fast but low diversity. <b>Sexual</b>: Two parents, genetic fusion. Slower but high genetic diversity.
<b>Interphase</b>: G1 (Growth), S (DNA Replication), G2 (Prep). <b>M Phase</b>: Mitosis (Nuclear division) + Cytokinesis (Cytoplasm division).
<b>Prophase</b>: Chromosomes condense, spindle forms. <b>Metaphase</b>: Chromosomes align at center. <b>Anaphase</b>: Sister chromatids separate. <b>Telophase</b>: Nuclei reform.
<b>Meiosis I</b>: Prophase I (Crossing Over), Metaphase I (Homologous pairs align), Anaphase I (Pairs separate), Telophase I. <b>Meiosis II</b>: Prophase II, Metaphase II, Anaphase II (Sister chromatids separate), Telophase II (4 haploid cells).
Division of cytoplasm. <b>Animal Cells</b>: Cell membrane pinches in (Cleavage Furrow). <b>Plant Cells</b>: Cell plate forms midway and develops into cell wall.
Controlled by <b>Regulatory Proteins</b>. <b>Internal Regulators</b> (e.g., Cyclins) respond to events inside cell. <b>External Regulators</b> (e.g., Growth Factors) respond to events outside cell (wound healing). <b>Apoptosis</b>: Programmed cell death.
Uncontrolled cell growth due to gene defects (e.g., <b>p53</b>). <b>Tumors</b>: Benign (non-cancerous) or Malignant (cancerous). <b>Treatments</b>: Surgery, Radiation, Chemotherapy.
<b>Differentiation</b>: Cells become specialized. <b>Stem Cells</b>: Unspecialized cells. <b>Totipotent</b> (can form any cell), <b>Pluripotent</b> (most body cells), <b>Multipotent</b> (limited types).
Reduction division for sexual reproduction. Produces 4 haploid (N) gametes from 1 diploid (2N) cell. Two rounds of division: Meiosis I and II.
<b>Meiosis I</b>: Homologous pairs separate. <b>Crossing Over</b> (Prophase I) increases diversity. <b>Meiosis II</b>: Sister chromatids separate (like mitosis).
<b>Nondisjunction</b>: Failure of chromosomes to separate. <b>Trisomy 21</b>: Down Syndrome (3 copies of ch 21). <b>Karyotype</b>: Image of chromosomes used to detect abnormalities.
Practice quiz
Why do cells typically remain small rather than growing indefinitely large?
- Larger cells require less energy.
- As cells grow, their surface area to volume ratio decreases, making nutrient exchange less efficient.
- DNA replication becomes too fast in large cells.
- Large cells are more prone to viral infections.
Answer: As cells grow, their surface area to volume ratio decreases, making nutrient exchange less efficient.
A bacterial colony rapidly reproduces through binary fission. This is an example of asexual reproduction. What is a key characteristic of the offspring produced this way?
- They have high genetic diversity.
- They are genetically identical to the parent.
- They require two parents.
- Their reproduction rate is slower than sexual reproduction.
Answer: They are genetically identical to the parent.
During which phase of the cell cycle does DNA replication occur?
- G1 phase
- S phase
- G2 phase
- M phase
Answer: S phase
A scientist observes a cell under a microscope where chromosomes are lined up precisely at the center of the cell. Which phase of mitosis is this cell most likely in?
- Prophase
- Metaphase
- Anaphase
- Telophase
Answer: Metaphase
Which event, crucial for increasing genetic diversity, occurs during Prophase I of meiosis?
- Sister chromatids separate.
- Homologous chromosomes align at the metaphase plate.
- Crossing over between homologous chromosomes.
- The nuclear envelope reforms around two sets of chromosomes.
Answer: Crossing over between homologous chromosomes.
How does cytokinesis in plant cells differ from cytokinesis in animal cells?
- Plant cells form a cleavage furrow, while animal cells form a cell plate.
- Plant cells form a cell plate, while animal cells form a cleavage furrow.
- Plant cells undergo nuclear division, while animal cells do not.
- Cytokinesis only occurs in animal cells.
Answer: Plant cells form a cell plate, while animal cells form a cleavage furrow.
Cyclins are a type of regulatory protein that respond to events inside the cell. What is their primary role in the cell cycle?
- To promote programmed cell death (apoptosis).
- To signal cells to speed up division in response to external growth factors.
- To regulate the timing of the cell cycle in eukaryotic cells.
- To repair damaged DNA before replication.
Answer: To regulate the timing of the cell cycle in eukaryotic cells.
Cancer is characterized by uncontrolled cell growth. Which gene, when defective, is often associated with this uncontrolled division?
- The gene for insulin production.
- The p53 gene.
- The gene for hemoglobin.
- The gene for chlorophyll.
Answer: The p53 gene.
A stem cell that has the ability to develop into any type of cell in the body, including the cells that form the placenta and embryonic tissues, is described as:
- Pluripotent
- Multipotent
- Totipotent
- Unipotent
Answer: Totipotent
Meiosis is a reduction division process. If a diploid organism has $2N = 46$ chromosomes in its somatic cells, how many chromosomes would be found in its haploid gametes after meiosis?
- $2N = 46$
- $N = 23$
- $4N = 92$
- $N = 46$
Answer: $N = 23$
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