Mitosis Flashcards
What is the role of mitosis?
Form of cell division that produces identical cells, there are four stages of mitosis: prophase, metaphase, anaphase and telophase.
Outline what happens in Prophase
- Chromosomes condense, becoming visible: 2 sister chromatids joined at centromere)
- Centrioles move to opposite poles of cells & mitotic SF form.
- Nuclear envelope & nucleolus is break down = chromosomes free in cytoplasm
Outline what happens during Metaphase
Sister chromatids line up at cell equators attached to the mitotic spindle by their centromeres
Outline what happens during Anaphase
- Spindle rivers contract = Centromeres divide
- 👯♀️ chromatids separate into 2 rusticity chromosomes & pulled to opposite poles of cell (look V shaped both ends)
- SF break down
Outline what happens during Telophase
- Chromosomes decondense, becoming invisible again.
- New nuclear envelopes form around each set of chromosomes = 2 New nuclei, each with 1 copy of each chromosome
Outline what happens during Interphase
G1 = Cell synthesises proteins eg tubulin for SF & cell doubles
S PHASE = 🧬 replicates and chromosomes consist of 2 sister chromatids joined together by centromeres
G2 = organelles divide and cells keep growing and proteins needs for the next cell division
Cytokinesis
during cytokinesis the parent and replicated organelles move to opposite sides of the cell and the cytoplasm divides thus producing two daughter cells.
Importance of Mitosis
- Growth: all cells produced are identical so organisms can grow using mitosis.
- Repair: all cells produced are identical so organisms can replace dead tissues using mitosis.
- Reproduction: some single-celled organisms, like yeast, reproduce by dividing into two identical daughter cells by mitosis.
What is the process in which prokaryotic cells divde.
Binary fission
Steps of binary fission:
- The circular DNA in the cells replicates and both copies attach to the cell membrane. Plasmids also replicate.
- The cell membrane then begins to grow between the two DNA molecules and begins to pinch inwards, dividing the cytoplasm in two.
- A new cell wall forms between the two DNA molecules dividing the original cell. The identical daughter cells each have a single copy of the circular DNA and a variable number of copies of the plasmids
Why do viruses not undergo cell divison.
viruses are non-living - following the injection of their
nucleic acids into another cell, the infected host cell replicates the virus particles.
Stages of mitosis - Mitosis
Metaphase
The chromosomes line up along the mid-line of the cell.
Stages of mitosis - Anaphase
Anaphase
The chromosomes break into two chromatids - these sister chromatids separate at the centromere.
Stages of mitosis - Telophase
Telophase
The chromatids reach the opposite poles and begin to decondense, becoming chromosomes again.
Stages of mitosis - Prophase
Prophase
The nuclear envelope breaks down and the nucleolus disappears. Chromosomes are left floating in cytopla
Simple steps for investigating mitosis
- Prepare sample
- Cut the root tipes from meristem
- Stain the root tips
- Squash the root tips
- View sample at 400x power under light microscope.
What is the Mitosis index
is used to work out the proportion of cells in the sample that are in mitosis.
Equation for Mitotic index
Mitotic index = number of cells in mitosis ÷ total number of cells
How can a cell size be measured?
using a micrometer and graticule.
Somatic cell
A cell that contain two sets of chromosomes (one inherited from the father and the other inherited from the mother) known as diploid number 2N, while the gametes (male sperms and female ova) contain the haploid number N.
Diploid
a cell that contain two copies of each chromosome.
Haploid
a cell that contains a single set of chromosomes. eg gametes sperm and egg cell
Compare and contrast a human somatic cell to a human gamete.
A-A* (AO3/4)
Somatic cells have 46 chromosomes and are diploid whereas gametes have half as many chromosomes as found in somatic
How do microtubules connect to chromosomes?
Microtubules bind to a protein complex on each chromosome, known as a kinetochore.
The kinetochores are located at the centrosome of each chromosome. This is a region of the DNA which the kinetochore proteins bind to.
