Mitosis and The Cell Cycle Flashcards
How are cells made?
Through cell division
How do prokaryotic cells divide?
Binary Fission
Types of eukaryotic cell division (2)
- Mitosis
- Meiosis
Mitosis definition
When a parent cell divides into 2 daughter cells with identical copies of DNA and the same number of chromosomes as the parent
Meiosis definition
When a parent cell divides into 4 daughter cells that each contain half the number of chromosomes in the parent cell
TRUE/FALSE: All multicellular organisms can divide
False e.g. neurones
Why shouldn’t cells divide continuously?
It may lead to uncontrolled cell division which can lead to cancer and brain tumours
Stages of the cell cycle
- Interphase
- Nuclear division (Mitosis)
- Cell division
Interphase
- Occupies most of the cycle in a 3-step process:
- Gap Phase 1: Proteins required for organelles are synthesised
- Synthesis Phase 1: DNA replication which doubles the mass
- Gap Phase 2: Organelles grow and divide, ATP levels increase
Nuclear division (Mitosis)
The nucleus divides into two or four, where each cell contains half the chromosomes of a complete nucleus
Cell division
Cytokinesis AKA division of cytoplasm where the cell divides into two or four daughter cells
How long does the cell cycle typically take?
24 hours
Stages of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
The chromosomes thicken and shorten by supercoiling.
The nuclear envelope disappears.
The centrioles form a spindle network, separate and move to opposite poles of the cell
Metaphase
The chromosomes move to the equator of the cell.
The spindle fibres attach to the centromeres.
Anaphase
The spindle fibres contract, separating the sister chromatids.
The individual chromatids are pulled towards the poles - they are now chromosomes.
Telophase
A nuclear envelope appears around each set of chromatids to form two new nuclei
The chromatids uncoil and the spindle fibres disintegrate
The cell surface membrane starts to invaginate at the equator of the cell
Mitotic index
The proportion of cells in a population undergoing mitosis
Formula for mitotic index
Number of cells undergoing mitosis/Total number of cells observed
How do cancer treatments control cell division?
Many treatments prevent DNA replication or interfere with metaphase by inhibiting spindle formation
How does chemotherapy stop uncontrolled cell division?
They disrupt the cell cycle in all dividing cells but have a greater effect on rapidly dividing cells
How does a virus replicate?
They do not divide but inject their nucleic acid into a host cell which synthesises viral nucleic acid and proteins and assembles virus particles
How does Binary Fission happen?
- Replication of the circular DNA and of plasmids in the cytoplasm
- Division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of any plasmid
