Mitosis and The Cell Cycle
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of chromosomes and the function of the nucleus to explain how genetic material is replicated and divided.
What are chromosomes?
Long coiled strands of DNA
How many chromosomes are in a human body cell?
46 (23 pairs)
Where is the DNA found in a prokaryote?
Cytoplasm
Topic Explainer Video
Check out this @JoeDoesBiology video that explains mitosis and the cell cycle, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
The Cell Cycle and Mitosis
Cell division by mitosis is important in the growth and development of multicellular organisms. It is used for growth, replacing cells, repairing tissues and, in some instances, for reproduction - this is called asexual reproduction.
The Cell Cycle
The cell cycle is the series of stages a cell goes through to grow and divide.
Main Stages:
1. Interphase (longest stage)
- The cell grows.
- DNA is replicated (each chromosome is copied).
- Sub-cellular structures, such as mitochondria and ribosomes, are duplicated.
2. Mitosis
- The nucleus divides to form two genetically identical nuclei.
3. Cytokinesis
- The cytoplasm divides, forming two new genetically identical cells. We call these cells ‘daughter cells’.
Mitosis: Step-by-Step
Remember, 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.
Chromosomes condense and become visible.
- Nuclear membrane breaks down.
- Chromosomes line up in the middle of the cell.
- One set of chromosomes is pulled to each opposite end of the cell.
- New nuclear membranes form around each set of chromosomes.
Finally, in cytokinesis, the cytoplasm and cell membranes divide to form two genetically identical cells.
Mitosis Summary
|
Feature |
Detail |
|
Number of divisions |
1 |
|
Cells produced |
2 daughter cells |
|
Chromosome number |
Diploid (full number of chromosomes) |
|
Genetic similarity |
Genetically identical to each other and the parent cell |
|
Purpose |
Growth, repair of tissues, replacement of cells, asexual reproduction |
No answer provided.
Binary Fission (Prokaryotic Cell Division)
Function: Binary fission is the process by which prokaryotic cells (like bacteria) divide.
Because prokaryotes do not have a nucleus they cannot divide by mitosis.
During binary fission, the prokaryotic DNA is replicated and the cytoplasm and cell membranes divide.
Key Terms
- Interphase – stage of cell growth and DNA replication.
- Mitosis - Division of the nucleus.
- Cytokinesis – division of the cytoplasm and cell membranes.
No answer provided.
Exam Tips
Lots of questions require you to know that mitosis produces genetically identical cells.
You need to describe the process of mitosis using the exact wording on your specification, including the key points:
- Chromosomes line up in the middle of the cell.
- One set of chromosomes is pulled to each opposite end of the cell.
- New nuclear membranes form around each set of chromosomes.
No answer provided.
Practice Question
Describe what happens to chromosomes during mitosis. (4 marks)
Model Answer:
- Chromosomes line up in the middle of the cell.
- One set of chromosomes is pulled to each opposite end of the cell.
- So each daughter cell is diploid / has a full set of chromosomes.
- New nuclear membranes form around each set of chromosomes.
More Practice
Try to answer these practice questions from the TikTok videos on your own, then watch the videos to see how well you did!