IB Diploma · Biology D2.1
IB Biology D2.1: Cell & Nuc. Div. — Practice Questions & Answers
IB Biology D2.1 study notes: mitosis, cytokinesis, the cell cycle, cyclins and the link between uncontrolled division and cancer.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
How are new cells generated in living organisms?
- IV. Cells can spontaneously generate from non-living organic matter under specific environmental conditions
- II. Mitosis is the primary process for generating new somatic cells for growth, tissue repair, and asexual reproduction
- I, II, and III only
- II and IV only
- I. New cells arise exclusively from the division of pre-existing cells through processes like mitosis and meiosis
- All I, II, III and IV
- III. Meiosis is the process responsible for producing gametes (sperm and egg cells) for sexual reproduction
- I and II only
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WhyNew cells arise by mitosis, meiosis, and binary fission, all producing cells from existing cells.
2
Multiple choice
What is cytokinesis?
- Condensation of chromosomes.
- Division of the nucleus.
- Replication of DNA.
- Splitting of cytoplasm in a parent cell between daughter cells.
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WhyCytokinesis is the division of the parent cell's cytoplasm between the two daughter cells.
3
Multiple choice
Which of the following statements accurately describe how cytokinesis (cytoplasmic division) occurs in animal cells?
- I. A cleavage furrow forms, which is an indentation in the cell surface
- III. The contractile ring tightens, pinching the cell into two separate daughter cells
- II. A contractile ring, composed of actin and myosin filaments, forms just inside the plasma membrane
- I, II, and III only
- I and II only
- IV. A cell plate forms in the middle of the cell, growing outwards to divide the cytoplasm
- II and IV only
- All I, II, III and IV
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WhyIn animal cells cytokinesis uses a contractile ring that pinches the membrane inward to form a cleavage furrow.
4
Multiple choice
How does cytokinesis occur in plant cells?
- A ring of actin and myosin proteins pinches the cell membrane.
- Microtubules pull chromosomes apart.
- Exocytosis of the cell membrane.
- Vesicles assemble sections of membrane and cell wall.
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WhyIn plant cells vesicles fuse at the centre to build a cell plate that becomes new membrane and wall.
5
Multiple choice
Is cytokinesis always equal?
- Independent of cell type.
- Usually, but not always.
- Always equal.
- Always unequal.
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WhyCytokinesis is usually equal but can be unequal, as in oogenesis or yeast budding.
6
Multiple choice
What is an example of unequal cytokinesis?
- Oogenesis in humans.
- Binary fission in bacteria.
- Mitosis in skin cells.
- Meiosis in sperm cells.
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WhyIn oogenesis, unequal cytokinesis gives one large egg and small polar bodies with little cytoplasm.
7
Multiple choice
What is another example of unequal cytokinesis?
- Binary fission in archaea.
- Meiosis in plant cells.
- Budding in yeast.
- Mitosis in plant cells.
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WhyBudding in yeast is unequal cytokinesis, producing a small daughter cell from the larger parent.
8
Multiple choice
What is the role of mitosis in eukaryotes?
- Maintains chromosome number and genome of cells.
- Produces haploid cells.
- Halves the chromosome number.
- Generates genetic diversity.
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WhyMitosis maintains the chromosome number and genome, producing genetically identical daughter cells.
9
Multiple choice
What is the role of meiosis in eukaryotes?
- Occurs in somatic cells.
- Produces diploid cells.
- Maintains chromosome number and genome of cells.
- Halves the chromosome number and generates genetic diversity.
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WhyMeiosis halves the chromosome number and generates genetic diversity for sexual reproduction.
10
Multiple choice
Why is DNA replication a prerequisite for mitosis and meiosis?
- To speed up cell division.
- To ensure each daughter cell receives a complete set of chromosomes.
- To produce anucleate cells.
- To increase genetic diversity.
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WhyReplication doubles the DNA first so each daughter cell can receive a complete set of chromosomes.
Key terms in Cell & Nuc. Div.
Cell cycle: The ordered sequence of growth and division events a cell passes through, consisting of interphase and the M phase.
Interphase: The active phase between divisions, comprising G<sub>1</sub>, S and G<sub>2</sub>, during which the cell grows and replicates its DNA.
Mitosis: Nuclear division producing two genetically identical daughter nuclei with the same chromosome number as the parent.
Sister chromatids: The two identical copies of a chromosome produced by DNA replication, joined at a centromere until anaphase.
Cytokinesis: Division of the cytoplasm after mitosis, forming two separate cells; differs between animal and plant cells.
Cyclin: A regulatory protein whose changing concentration controls progression through the stages of the cell cycle.
Mutagen: An agent that increases the rate of mutation; a carcinogen is a mutagen that can cause cancer.
Tumour: A mass of cells produced by uncontrolled division; benign if localised, malignant if its cells spread (metastasise).
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