AQA GCSE Cell Cycle and Mitosis (Biology)
Cell cycle and Mitosis
The cell cycle is the sequence of stages that occur when a cell divides.
There are 3 main stages to the cell cycle.
Interphase
This is the longest phase and prepares the cell for division.
DNA is replicated to double the amount of genetic material in the cells. During the replication two copies of each chromosome are formed as shown below. The chromosomes will remain attached to each other for the moment.
During interphase the cell will grow in size and the number of ribosomes and mitochondria will increase.
Mitosis
The nuclear membrane will distintegrate, chromosomes briefly align along the equator of the cell before being pulled to opposite ends of the cell.
See the diagram below.
Cytokinesis.
Cytokinesis is the splitting of the cytoplasm, at the same time the cell membrane will pinch inwards to allow for the formation of two new cells. Nuclear membrane will form around each set of chromsomes in both cells.
This will result in the formation of 2 genetically identical daughter cells being formed.
Importance of mitosis for organisms.
Mitosis is important in multicellular organisms because:
Growth of the organism: It increases the number of cells, allowing an organism to grow from a single fertilised egg into a mature individual.
Repair of tissues: It replaces damaged or worn-out cells (e.g., skin cells, blood cells).
Asexual reproduction (in some organisms): It produces genetically identical offspring.
Development: It allows tissues and organs to form and develop correctly during embryonic development when the cells divide by mitosis.
Practice Question
1.State what is meant by the term cell cycle
2.Name the three stages of the cell cycle
3.Mitosis is important to multicellular organsism. Explain why.