Cell Division, Reproduction & Development — Chapter Practice, Grade 10

Connect chromosome continuity, variation, regulated growth, and specialization.

Problem 1

In the standard model without new copying errors, what is the main result of mitosis followed by cytokinesis?
  1. Two genetically identical daughter cells
  2. Four sex cells with half the DNA
  3. A cell with double the normal chromosome number
  4. A finished protein
Answer and explanation

Two genetically identical daughter cells

Mitosis produces two daughter cells genetically identical to the parent, used for growth and repair.

Problem 2

Which is the correct order of the phases of mitosis?
  1. Anaphase, Metaphase, Prophase, Telophase
  2. Prophase, Metaphase, Anaphase, Telophase
  3. Metaphase, Prophase, Anaphase, Telophase
  4. Telophase, Anaphase, Metaphase, Prophase
Answer and explanation

Prophase, Metaphase, Anaphase, Telophase

The order is Prophase, Metaphase, Anaphase, Telophase — remembered as PMAT.

Problem 3

Starting from a single cell, how many cells exist after 5 rounds of mitosis?
Answer and explanation

32 cells

Each round doubles the count: 2^5 = 32 cells.

Problem 4

Explain why a cell must copy its DNA during interphase before it divides by mitosis.
Answer and explanation

Copying the DNA first means there are two complete sets of chromosomes to distribute, so when the cell splits, each daughter cell receives a full, identical set rather than half of one.

Problem 5

How is cancer related to the cell cycle?
  1. Cells begin making sex cells instead of body cells
  2. DNA is no longer copied before division
  3. Mutations damage the genes that control the cell cycle, so cells divide uncontrollably and ignore normal stop signals
  4. The cell cycle stops completely and no cells ever divide again
Answer and explanation

Mutations damage the genes that control the cell cycle, so cells divide uncontrollably and ignore normal stop signals

Cancer arises when the checkpoint-control genes are mutated, letting cells divide out of control instead of stopping when they should.

Problem 6

A diploid cell has 12 chromosomes before replication. How many chromosomes does each daughter cell normally have after mitosis and cytokinesis? Explain the reasoning in your own words.
Answer and explanation

Each daughter normally has 12 chromosomes in this model.

Replication makes sister chromatids without changing the stated chromosome number.

Normal separation gives each daughter the original set size.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

A diploid cell has 12 chromosomes. What count is expected after normal mitosis in each daughter? Show the reasoning, not just the conclusion.
Hints

Chromatid doubling after replication is not a doubling of chromosome count when counted by centromeres.

Answer and explanation

12 chromosomes in each daughter.

Problem 8

Why do checkpoints matter before division?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

They help coordinate replication, DNA integrity and segregation; failures can permit abnormal growth or chromosome errors.

Problem 9

Checkpoints regulate progression instead of promising perfect copyingCheckpoints regulate progression instead of promising perfect copyingDNA damage / signalsCheck before progressionRepair, pause or stopnot automatic divisionRegulation involves multiple pathways and responses.
Original control-decision abstraction, not a cancer diagnostic model or exhaustive checkpoint network.
Interpret the supplied visual. Does the mere observation of cell division establish failed regulation?
Answer and explanation

No. Division is also part of normal growth and renewal; interpretation needs the conditions, tissue behavior and regulatory evidence.

A checkpoint is a regulatory interaction that coordinates progression with conditions such as DNA integrity and spindle attachment. Repair, arrest and other responses can limit the propagation of damage. Cancer involves altered growth regulation and additional changes in cellular behavior; a single missed checkpoint is not a complete diagnosis or explanation of every tumor. Rate and timing differ among tissues. A cell-cycle diagram should show controlled transitions and distinguish damaged DNA, attempted repair and the later fate of the cell.

No. Division is also part of normal growth and renewal; interpretation needs the conditions, tissue behavior and regulatory evidence.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 10

A diploid model starts with 10 chromosomes. Track chromosomes, chromatids and daughter-cell chromosome number through replication and normal mitosis/cytokinesis.
Answer and explanation

After S phase there are 10 replicated chromosomes and 20 chromatids; during separation each former chromatid becomes a chromosome. Each daughter receives 10 chromosomes, preserving diploidy in the model.

After S phase there are 10 replicated chromosomes and 20 chromatids; during separation each former chromatid becomes a chromosome. Each daughter receives 10 chromosomes, preserving diploidy in the model.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 11

The main job of meiosis is to produce
  1. two identical body cells for growth
  2. new proteins from mRNA
  3. an exact copy of a single chromosome
  4. four haploid gametes (sex cells) with half the chromosome number
Answer and explanation

four haploid gametes (sex cells) with half the chromosome number

Meiosis makes four haploid gametes, each with half the parent cell's chromosome number.

Problem 12

A human body cell has 46 chromosomes. How many chromosomes are in a normal human egg or sperm cell?
Answer and explanation

23 chromosomes

Gametes are haploid, carrying half of 46, which is 23.

Problem 13

Crossing over increases genetic variation because it
  1. exchanges matching segments between homologous chromosomes, creating new allele combinations
  2. copies a chromosome exactly
  3. destroys half of a cell's genes
  4. turns a body cell into a gamete without any division
Answer and explanation

exchanges matching segments between homologous chromosomes, creating new allele combinations

In crossing over, homologous chromosomes swap segments, producing chromosomes with new mixes of alleles.

Problem 14

Explain why meiosis (followed by fertilization) keeps a species' chromosome number constant from one generation to the next.
Answer and explanation

Meiosis halves the chromosome number when it makes gametes, so each gamete carries only one set. When two gametes join at fertilization, the two halves add back up to the full number, keeping it constant instead of doubling each generation.

Problem 15

An organism has 5 pairs of homologous chromosomes. From independent assortment alone, how many genetically different gametes are possible?
Answer and explanation

32 gametes

Each of the 5 pairs assorts independently in 2 ways: 2^5 = 32.

Problem 16

A species has diploid number 16. What is the normal gamete number and zygote number after fertilization? Explain the reasoning in your own words.
Answer and explanation

Gametes have 8 chromosomes; the zygote has 16.

The gamete has one set, half of 16: 8.

Two normal gametes combine: 8+8=16.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 17

For 2n=14, give n and the count after fusion of two normal gametes. Show the reasoning, not just the conclusion.
Hints

Halving refers to homologous sets, not arbitrary removal of any chromosomes.

Answer and explanation

n=7; fertilization restores 14.

Problem 18

How can crossing over generate new combinations without making new alleles?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

It exchanges segments between homologous chromosomes, rearranging existing variants.

Problem 19

Compare set number, DNA copies and final products separatelyCompare set number, DNA copies and final products separatelyChromosome counts in a supplied 2n = 4 modelStarting diploid nucleus4After DNA copying4After meiosis I /nucleus2After meiosis II /nucleus2DNA-copy counts differ: 4 → 8 → 4 → 2 per nucleus.
Original chromosome-count account for a two-pair model, not human numbers or all possible errors.
Interpret the supplied visual. Why would “meiosis halves each chromosome” be inaccurate?
Answer and explanation

It reduces chromosome-set number by segregation; chromosomes remain whole structures, with possible exchanged regions.

In the supplied 2n=4 model, DNA replication gives eight chromatids within four replicated chromosomes. After meiosis I each nucleus has two replicated chromosomes and four chromatids; after meiosis II each normally has two unreplicated chromosomes. Typical mitosis instead preserves the starting ploidy in daughter nuclei. This distinguishes division number, chromosome number and DNA content. The standard model predicts variation but does not guarantee that every meiotic product must be different at every locus; sequence, pairing and chance constrain the actual combinations.

It reduces chromosome-set number by segregation; chromosomes remain whole structures, with possible exchanged regions.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 20

A diploid model has 2n=6. Give chromosome and chromatid counts after S phase, after meiosis I per nucleus and after meiosis II per nucleus.
Answer and explanation

After S: 6 chromosomes and 12 chromatids. After I: 3 replicated chromosomes and 6 chromatids per nucleus. After II: 3 unreplicated chromosomes per nucleus. The standard model includes one replication before two divisions.

After S: 6 chromosomes and 12 chromatids. After I: 3 replicated chromosomes and 6 chromatids per nucleus. After II: 3 unreplicated chromosomes per nucleus. The standard model includes one replication before two divisions.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 21

Different cell functions commonly reflect…
  1. different gene-expression patterns
  2. complete removal of all shared DNA
  3. lack of proteins in most tissues
  4. only cell color
Answer and explanation

different gene-expression patterns

Expression determines which products are made.

Problem 22

Why can a checkpoint delay division after DNA damage?
Answer and explanation

A delay permits repair or other responses before damaged information is passed on.

Problem 23

Distinguish healthy growth from uncontrolled proliferation.
Answer and explanation

Healthy growth is coordinated with tissue needs and regulation; uncontrolled proliferation bypasses important controls.

Problem 24

Why can a neuron and a muscle cell have different functions despite sharing much of the same DNA? Explain the reasoning in your own words.
Answer and explanation

Differential gene expression helps create functional differences without requiring different basic genomes.

Different gene-expression patterns produce different proteins.

Those proteins support distinct structures and activities.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 25

What distinguishes controlled cell division from uncontrolled proliferation? Show the reasoning, not just the conclusion.
Hints

Compare gene presence with gene use.

Answer and explanation

Regulatory signals and checkpoints normally constrain division; disrupted controls can allow excessive proliferation.

Problem 26

Why can a DNA change in a cell-cycle regulator matter to tissue organization?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

It may alter growth or division control, depending on the change and biological context.

Problem 27

A cell count combines division, loss and changes in stateA cell count combines division, loss and changes in stateCell count in a supplied culture model1001201401601800123DaysPopulation APopulation B
Original illustrative culture-count records, not a tissue-specific clinical growth curve.
Interpret the supplied visual. Can a nearly steady count mean no cells divided or died?
Answer and explanation

No. Birth and loss can nearly balance; direct tracking or separate rate measurements are needed.

Turnover combines production and removal of cells within a defined population. A rising culture count can reflect division exceeding loss; it does not directly show the rate of one cell or whether descendants have specialized. Different tissues maintain different renewal patterns, and many cells can pause division. Migration, death and measurement boundaries matter when comparing counts. A useful explanation links signals, checkpoint conditions and measured state rather than assuming every slowly growing sample has the same defect.

No. Birth and loss can nearly balance; direct tracking or separate rate measurements are needed.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 28

Two samples share the same DNA sequence at a tested gene but show different RNA amounts and cell functions. Explain a possible mechanism and one limit of the evidence.
Answer and explanation

Different regulation can change expression without changing that tested sequence. Other genes, processing and cellular conditions can contribute; matching one gene does not establish complete genome identity or a unique cause.

Different regulation can change expression without changing that tested sequence. Other genes, processing and cellular conditions can contribute; matching one gene does not establish complete genome identity or a unique cause.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 29

A diploid animal has 18 chromosomes. How many are in a normal gamete?
Answer and explanation

9 chromosomes

Meiosis halves the diploid count.

Problem 30

Which is needed for development beyond increasing cell number?
  1. Differentiation and organization
  2. All genes permanently switching off
  3. Loss of every membrane
  4. Elimination of all signals
Answer and explanation

Differentiation and organization

Cells must acquire coordinated roles and structures.

Problem 31

Can asexual descendants ever differ genetically?
Answer and explanation

Yes. Mutations and other genome changes can introduce differences.

Problem 32

Why does a multicellular embryo need cell signaling as well as cell division? Explain the reasoning in your own words.
Answer and explanation

Signaling organizes specialized tissues rather than only a larger pile of cells.

Division increases cell number.

Signals help coordinate which cells differentiate, move or grow in particular locations.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 33

What is one biological advantage of sexual reproduction for variation? Show the reasoning, not just the conclusion.
Hints

Increasing cell number alone does not explain tissue pattern.

Answer and explanation

Combining alleles from parents and meiotic processes generates new genetic combinations.

Problem 34

Does a developmental outcome depend only on DNA sequence?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. Gene regulation, cellular interactions and environmental conditions also influence development.

Problem 35

Development coordinates cell state with spatial organizationDevelopment coordinates cell state with spatial organizationPosition, signals and gene regulation influence cell fateStructure formation combines differentiation, movement and selective loss.
Original positional cell-state model; colors denote illustrative states rather than actual germ layers or a measured signal gradient.
Interpret the supplied visual. Does a positional difference in cell fate necessarily imply a mutation occurred at that location?
Answer and explanation

No. Different signals and regulatory states can change development without changing the underlying DNA sequence.

A developmental signal affects cell behavior in a spatial and temporal context. Different positions can expose otherwise related cells to different inputs, changing gene expression and fate. Morphogenesis is formation of biological shape through coordinated growth, movement, interactions and sometimes regulated cell loss. It is not only making more cells, and it does not mean DNA is deliberately rewritten in every location. The resulting structure needs functional relationships among tissues, so interpret cell markers together with position and behavior.

No. Different signals and regulatory states can change development without changing the underlying DNA sequence.

Response criteria

  • Read the structures, axes, directions and units correctly.
  • Connect the evidence with the biological mechanism.
  • Respect stated model assumptions and distinguish an observation from a further inference.

Problem 36

A supplied embryo model divides from 1 to 8 cells while total material is initially comparable. Explain cell number versus size, and how different cell fates could arise without new mutations.
Answer and explanation

Cleavage partitions material among more, smaller cells rather than requiring eightfold growth. Positional signals and gene regulation can change cell fate without new DNA-sequence changes; structure/function evidence must test those outcomes.

Cleavage partitions material among more, smaller cells rather than requiring eightfold growth. Positional signals and gene regulation can change cell fate without new DNA-sequence changes; structure/function evidence must test those outcomes.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the biological mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Browse all courses