Mitosis and the cell cycle — AQA GCSE Combined Science
Test yourself on Mitosis and the cell cycle with AQA GCSE practice questions.
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Mitosis and the cell cycle explained
The cell cycle is the sequence of events by which a cell grows, replicates its DNA and divides to form two genetically identical daughter cells.
Read the full explanation
It occurs in three main stages. First, the cell grows, increases its mass, replicates its DNA to form two copies of each chromosome, and increases the number of sub-cellular structures like mitochondria and ribosomes. Second, mitosis occurs: one set of chromosomes is pulled to each end of the cell and the nucleus divides. Finally, the cytoplasm and cell membranes divide to form two identical cells. You do not need to know the names of the specific phases of mitosis (prophase, metaphase, anaphase, telophase), just the overall process of chromosome separation and division.
During the cell cycle the genetic material is doubled and then divided into two identical cells.
Before a cell divides, its genetic material must be doubled so that each daughter cell receives a complete set of chromosomes. During interphase, DNA replication produces two identical copies of each chromosome, called sister chromatids, held together at a centromere. The amount of DNA in the nucleus is therefore doubled, although the chromosome number stays the same. In mitosis, the sister chromatids are separated so that one copy of each chromosome goes into each new nucleus. Cytokinesis then divides the cytoplasm, forming two genetically identical daughter cells with the same chromosome number as the parent. For example, a human body cell with 46 chromosomes replicates its DNA and divides by mitosis to produce two cells that each have 46 chromosomes.
Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
Before division, a cell must prepare so that each daughter cell receives everything it needs. During interphase, the cell grows, increasing its cytoplasm and making more sub-cellular structures. Ribosomes are needed for protein synthesis, and mitochondria supply the ATP required for the many reactions of division. The genetic material must also be copied: DNA replication produces two identical copies of every chromosome, each consisting of two sister chromatids held together. For example, a human body cell with 46 chromosomes replicates its DNA so that each chromosome now has two identical chromatids, while the chromosome number remains 46. This ensures that when the nucleus divides, each new cell receives a complete, identical set of chromosomes and enough organelles to function.
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Mitosis is the stage of the cell cycle in which the copied chromosomes are separated and the nucleus divides. The chromosomes, each consisting of two sister chromatids, line up at the equator of the cell. The chromatids are then pulled apart by spindle fibres, so that one complete set of chromosomes moves to each end of the cell. Once the sets are separated, a new nuclear membrane forms around each group and the nucleus divides, producing two genetically identical nuclei. For example, in a human cell with 46 chromosomes, each new nucleus receives 46 chromosomes identical to those of the parent cell. This process ensures genetic continuity and is essential for growth, repair and asexual reproduction.
Finally the cytoplasm and cell membranes divide to form two identical cells.
This statement describes the final stage of the cell cycle, after the genetic material has been replicated and the nucleus has divided. The cytoplasm divides (cytokinesis) and new cell membranes form, separating the cell contents into two daughter cells. Because each daughter cell receives an identical set of chromosomes, the two cells are genetically identical to each other and to the parent cell. For example, a human body cell with 46 chromosomes replicates its DNA, then divides so each new cell also has 46 chromosomes. This process supports growth, repair and asexual reproduction, and it is assessed by asking you to place the events in order and explain why the products are identical.
Students need to understand the three overall stages of the cell cycle but do not need to know the different phases of the mitosis stage.
This statement sets the depth of knowledge required for the cell cycle. You must understand its three overall stages: first, the cell grows and replicates its DNA so each chromosome is copied; second, the nucleus divides, distributing one complete set of chromosomes to each end of the cell; third, the cytoplasm and cell membranes divide to produce two genetically identical daughter cells. You do not need to name or describe the individual phases of mitosis, such as prophase, metaphase, anaphase and telophase. Assessment focuses on ordering the three stages, explaining the purpose of DNA replication and stating the outcome of the cycle, for example in a human cell with 46 chromosomes.
Cell division by mitosis is important in the growth and development of multicellular organisms.
Mitosis is a type of cell division that produces two genetically identical diploid cells from one parent cell. In multicellular organisms it underpins growth: an increase in cell number, not just cell enlargement, allows an organism to become larger. It also supports development, the process by which cells become organised into tissues and organs with specialised roles. For example, a root tip or shoot tip in a plant contains meristem cells that divide by mitosis, adding new cells behind the tip so the plant grows taller or longer. Similarly, in animals, mitosis replaces worn-out cells and repairs damaged tissue. Because the DNA is copied before division and each new cell receives a full set of chromosomes, the daughter cells can carry out the same functions as the parent cell.
Students should be able to recognise and describe situations in given contexts where mitosis is occurring.
To recognise where mitosis is occurring, look for situations involving growth, repair or replacement of body cells. Mitosis produces genetically identical diploid cells, so it happens when an organism needs more identical cells, not when gametes are being formed. In a plant, mitosis occurs in the meristems at root tips and shoot tips, where new cells are added for growth. In an animal, it occurs during growth of a young organism, healing of a cut or broken bone, and replacement of worn-out cells such as skin or blood cells. In a diagram or written context, clues include a parent cell dividing into two identical daughter cells, chromosomes being copied and separated, or a tissue increasing in cell number. If the context involves gametes or genetic variation, meiosis is more likely.
Your focus
- State the three main stages of the cell cycle in the correct order.
- Describe the key events of cell growth and DNA replication.
- Explain how mitosis produces two genetically identical daughter cells.
Show all 25 objectives
- Describe how genetic material is doubled during interphase.
- Explain how mitosis divides the genetic material into two identical cells.
- State that the daughter cells have the same chromosome number as the parent cell.
- Describe the events of interphase, including cell growth and DNA replication.
- Explain why ribosomes and mitochondria must increase in number before mitosis.
- State that DNA replication produces two identical copies of each chromosome without changing the chromosome number.
- Describe how one set of chromosomes is pulled to each end of the cell during mitosis.
- Explain that mitosis results in the formation of two genetically identical nuclei.
- Relate mitosis to growth, repair and asexual reproduction in multicellular organisms.
- Describe the final stage of the cell cycle in which the cytoplasm and cell membranes divide.
- Explain why the two daughter cells formed are genetically identical to each other and to the parent cell.
- Relate the outcome of the cell cycle to growth, repair or asexual reproduction in a named organism.
- Outline the three overall stages of the cell cycle in the correct order.
- Explain the importance of DNA replication before nuclear division.
- Describe the outcome of the cell cycle as two genetically identical daughter cells without naming individual phases of mitosis.
- State that mitosis produces two genetically identical diploid daughter cells from one parent cell.
- Explain how mitosis contributes to growth by increasing cell number in multicellular organisms.
- Describe how mitosis supports development by producing cells that form tissues and organs.
- Identify named locations, such as root tips and shoot tips, where mitosis occurs for growth.
- Identify situations involving growth, repair or replacement as contexts where mitosis occurs.
- Describe what is happening in a given context using the outcome of mitosis, including genetically identical diploid daughter cells.
- Distinguish between contexts involving mitosis and contexts involving meiosis, such as gamete formation.
Mitosis and the cell cycle exam tips
Marking Points
- Stage 1 involves cell growth, DNA replication to form two copies of each chromosome, and an increase in sub-cellular structures.
- Stage 2 is mitosis, where one set of chromosomes is pulled to each end of the cell.
- During mitosis, the nucleus divides.
- Stage 3 involves the division of the cytoplasm and cell membranes.
- The overall cell cycle produces two genetically identical daughter cells.
- DNA replication occurs during interphase, doubling the genetic material before division.
- Each replicated chromosome consists of two identical sister chromatids joined at a centromere.
- The chromosome number is maintained because each daughter cell receives one copy of every chromosome.
- Mitosis separates the sister chromatids so that each new nucleus gets a complete set of chromosomes.
- Cytokinesis divides the cytoplasm to form two separate daughter cells.
- The two daughter cells are genetically identical to each other and to the original parent cell.
- Interphase is the stage before mitosis in which the cell grows and carries out DNA replication.
- The cell increases its number of sub-cellular structures, including ribosomes and mitochondria, in preparation for division.
- Ribosomes are required for protein synthesis, and mitochondria release energy for the cell's activities, including division.
- DNA replication produces two identical copies of each chromosome, so each chromosome consists of two sister chromatids.
- After replication, the chromosome number is unchanged; each chromosome has been copied rather than the cell gaining extra chromosome sets.
- The copied chromosomes ensure that each daughter cell receives a complete and genetically identical set of genetic material.
- Mitosis is the part of the cell cycle in which the nucleus divides to form two genetically identical nuclei.
- The chromosomes line up and are separated so that one complete set of chromosomes is pulled to each end of the cell.
- Spindle fibres attach to the chromosomes and pull the sister chromatids apart.
- A nuclear membrane forms around each set of chromosomes, so two new nuclei are produced.
- Each daughter nucleus receives the same number and type of chromosomes as the parent cell.
- The separated chromosomes are genetically identical, which maintains genetic continuity.
- Cytokinesis is the division of the cytoplasm, occurring after the nucleus has divided.
- New cell membranes form around each set of cell contents, separating the two daughter cells.
- Each daughter cell receives an identical copy of the genetic material, so the cells are genetically identical.
- The two daughter cells are also identical to the original parent cell in chromosome number and DNA base sequence.
- In a human body cell, the parent cell and both daughter cells each contain 46 chromosomes.
- The final division produces two cells, not four, distinguishing mitosis from meiosis.
- The first overall stage involves cell growth and replication of DNA, producing two copies of each chromosome.
- The second overall stage is nuclear division, in which one set of chromosomes moves to each end of the cell.
- The third overall stage is division of the cytoplasm and cell membranes, forming two daughter cells.
- The outcome is two genetically identical cells, each with the same chromosome number as the parent cell.
- Naming or describing individual phases of mitosis is not required for this specification.
- The three stages can be applied to growth, repair and asexual reproduction.
- Mitosis produces two daughter cells from one parent cell.
- The daughter cells are genetically identical to each other and to the parent cell.
- Each daughter cell receives a complete set of chromosomes, so the cells are diploid.
- Growth in multicellular organisms involves an increase in cell number by mitosis as well as an increase in cell size.
- Development involves mitosis providing new cells that become organised into tissues and organs.
- In plants, mitosis occurs in meristems such as root tips and shoot tips, allowing growth in length.
- In animals, mitosis is involved in growth, repair of damaged tissues and replacement of cells.
- Recognise growth of a multicellular organism as a situation where mitosis occurs.
- Recognise repair of damaged tissue, such as healing a cut or mending a bone, as a situation where mitosis occurs.
- Recognise replacement of worn-out cells, such as skin or blood cells, as a situation where mitosis occurs.
- Identify meristems in root tips and shoot tips as plant regions where mitosis occurs.
- Describe the outcome of mitosis in the context: two genetically identical diploid daughter cells.
- Distinguish mitosis from meiosis by noting that mitosis does not produce gametes or genetic variation.
Examiner Tips
- 💡Describe the cell cycle in three distinct stages: growth/replication, mitosis (nuclear division), and cell division.
- 💡Remember to mention the increase in sub-cellular structures like mitochondria and ribosomes during the first stage.
- 💡Use the terms DNA replication, sister chromatids and genetically identical accurately in your answer.
- 💡State clearly that the chromosome number is maintained, not doubled, in the daughter cells.
- 💡Link the doubling of genetic material to interphase and the separation to mitosis when explaining the process.
- 💡Use the term interphase when describing the preparation stage before mitosis.
- 💡Link each sub-cellular structure to its function: ribosomes for protein synthesis and mitochondria for energy release.
- 💡When explaining DNA replication, state clearly that two identical copies of each chromosome are formed and that the chromosome number does not change.
- 💡Use the phrase 'one set of chromosomes is pulled to each end of the cell' when describing the key event of mitosis.
- 💡Distinguish clearly between mitosis (nuclear division) and cytokinesis (division of the cytoplasm).
- 💡When asked why mitosis is important, link it to growth, repair and asexual reproduction, and to the production of genetically identical cells.
- 💡Sequence the cell cycle clearly: DNA replication and growth, nuclear division, then cytoplasm and membrane division.
- 💡Use the phrase genetically identical and support it by referring to identical chromosomes or DNA.
- 💡Link the final division to a named purpose such as growth, repairing damaged tissue or asexual reproduction.
- 💡Learn a three-step sequence and use it to answer ordering or description questions.
- 💡State the purpose of DNA replication, namely that each daughter cell receives a complete copy of the genetic material.
- 💡If a question asks for detail beyond the three stages, keep your answer to the overall stages rather than inventing phase names.
- 💡Link mitosis explicitly to growth and development in the context given, rather than describing the stages of mitosis in isolation.
- 💡Use the phrase genetically identical when explaining the outcome of mitosis, and state that the chromosome number is maintained.
- 💡Give a named example, such as a plant root tip or shoot tip, to show where mitosis occurs for growth.
- 💡If asked to explain importance, refer to both growth and development, and mention repair or replacement where relevant.
- 💡Read the context carefully and look for keywords such as growth, repair, replacement, root tip or shoot tip.
- 💡When describing a situation, state what is dividing and why, for example a root tip cell dividing to add new cells for growth.
- 💡Use the phrase genetically identical diploid daughter cells to show understanding of the outcome of mitosis.
- 💡If a context mentions gametes or variation, explain that this indicates meiosis rather than mitosis.
Common Mistakes
- Thinking that mitosis is the whole cell cycle: correct this by stating that mitosis is only the nuclear division stage, while growth and cytoplasmic division are also parts of the cycle.
- Stating that the cell divides during the first stage: correct this by stating that the first stage is for growth and DNA replication, and division occurs later.
- Including the names of mitosis phases (prophase, metaphase, etc.): correct this by focusing only on the movement of chromosomes to each end of the cell and nuclear division.
- Saying the chromosome number doubles during interphase: correct this by stating that the DNA amount doubles but the chromosome number stays the same because the copies remain attached as sister chromatids.
- Thinking the daughter cells are genetically different: correct this by stating that mitosis produces genetically identical cells because each receives the same chromosome copies.
- Confusing DNA replication with protein synthesis: correct this by stating that replication copies DNA, whereas protein synthesis uses DNA instructions to build proteins.
- Thinking that the cell doubles its chromosome number during replication. Correction: the number of chromosomes stays the same; each chromosome is copied to form two identical chromatids.
- Confusing growth with cell division. Correction: growth and DNA replication occur during interphase before mitosis, not during mitosis itself.
- Believing that mitochondria and ribosomes are unimportant for division. Correction: mitochondria provide energy and ribosomes make proteins, both essential for the cell to divide successfully.
- Saying that the cell divides into two cells during mitosis. Correction: mitosis itself is nuclear division; the cytoplasm usually divides afterwards in cytokinesis.
- Thinking that the chromosomes are pulled to the ends before they have been copied. Correction: DNA replication occurs during interphase, so each chromosome already consists of two sister chromatids before mitosis begins.
- Believing that the daughter nuclei are genetically different. Correction: mitosis produces two nuclei that are genetically identical to each other and to the parent nucleus.
- Thinking the cytoplasm divides before the nucleus divides; correct this by stating that nuclear division occurs first, then cytokinesis.
- Believing the daughter cells are genetically different; correct this by explaining that DNA replication before division gives each cell an identical chromosome set.
- Confusing the products of mitosis with the four genetically different cells of meiosis; correct this by stating that mitosis produces two identical cells.
- Listing prophase, metaphase, anaphase and telophase as required knowledge; correct this by learning only the three overall stages.
- Treating DNA replication as part of nuclear division; correct this by placing replication in the first growth stage, before the nucleus divides.
- Describing the cell cycle as producing four cells; correct this by stating that it produces two genetically identical daughter cells.
- Thinking that mitosis produces gametes; correction: gametes are produced by meiosis, whereas mitosis produces body cells for growth and repair.
- Believing that daughter cells are genetically different; correction: mitosis produces genetically identical cells because the chromosomes are copied before division.
- Confusing growth with cell enlargement only; correction: growth in multicellular organisms also requires an increase in cell number by mitosis.
- Assuming mitosis halves the chromosome number; correction: the chromosome number stays the same, so diploid parent cells produce diploid daughter cells.
- Choosing gamete formation as an example of mitosis; correction: gametes are produced by meiosis, so gamete formation is not a mitosis context.
- Assuming any cell division is mitosis; correction: check whether the context involves growth, repair or replacement of body cells rather than gamete production.
- Ignoring the word identical when describing daughter cells; correction: mitosis produces genetically identical cells, which is why it is suitable for growth and repair.
- Confusing plant growth with mitosis occurring throughout the plant; correction: mitosis for growth occurs mainly in meristems such as root tips and shoot tips.