Mitosis Flashcards
What is a centromere
A small section of DNA and associated proteins that attaches the sister chromatids to each other
What does a chromosome consist of
- Replicated one = 2 chromatids each with a DNA sequence identical to the other
- AKA sister chromatids
What happens to the chromatids when the centromere splits
Each chromatid becomes an individual chromosome
What are the parts of the cell cycle
- Gap 1 ( G1 )
- Synthesis ( S )
- Gap 2 ( G2 )
- Mitotic stage ( M )
Explain what happens in G1
This is normally the longest period of the cell cycle and stretches from the time of cytokinesis and the next round of DNA synthesis
Explain what happens in G2
This is the preparatory stage for mitosis. Organelles are replicated and proteins required in mitosis, e.g. for the formation of microtubules, are produced
Explain what happens in S
This refers to the phase in which the chromosomes are duplicated, i.e. DNA synthesis
Explain what happens in M
This involves the division of chromosomes and the subsequent cytokinesis
Explain G1 checkpoint
- Cell cycle checkpoint
- Apoptosis will occur is DNA is damaged and cannot be repaired
- Otherwise the cell is committed to divide
- Check cell and DNA for damage
Explain M checkpoint
- Spindle assembly checkpoint
- Mitosis will not continue if chromosomes are not properly aligned
Explain what needs to be ensured in the cell for DNA replication and cell division
No problems with cell
DNA isn’t damaged
Replicated properly
Explain G2 checkpoint
- Mitosis checkpoint
- Mitosis will occur if the DNA has replicated properly
- but if there’s any problems with DNA, apoptosis will occur
What type of cells undergo cell division
Normal and undamaged cells
Explain mitosis fully
- Main purpose of mitosis in eukaryotes is growth and the repair of damaged tissue
- This involves the somatic cells, i.e. All cells not involved in reproduction
- There are, however, plant, animal, fungi and prokaryotes that reproduce through mitosis and this is called asexual reproduction
What are daughter cells
- Outcome of mitosis which are identical to parent cell ( exact same number of chromosomes as parent cell )
How is the number of chromosomes in daughter cell the same as in parent cell
Chromosome number of parent cell is duplicated before it is halved again
What does duplication of chromosomes result in
2 sister chromatids held together by the centromere
Explain early prophase
- Centrosomes have duplicated
- Chromatin is condensing into chromosomes and the nuclear envelope is fragmenting
Explain prophase fully
- Chromosomes become shorter and thicker into distinct individual chromosomes,
- Nuclear membrane disintegrates (prometaphase), nucleolus disappears,
- Centrioles duplicate and migrate to opposite poles and the spindle apparatus begins to form.
- Chromosomes are seen as two sister chromatids held together at the centromere
- Spindle fibers then attach to kinetochores - one kinetochore for each sister chromatid – complex of proteins
Explain metaphase fully
- Centromeres of duplicated chromosomes are aligned at the metaphase plate ( centre of fully formed spindle )
- Kinetochore spindle fibres attached to the sister chromatids come from opposite spindle poles
- The chromosomes are arranged on the equatorial plane of the spindle
Explain anaphase
- Sister chromatids part and become daughter chromosomes that move toward the spindle poles
- Each pole receives the same number and kind of chromosomes as the parent cell
Explain telophase
- Daughter cells are forming as nuclear envelope and nucleoli reappear
- Chromosomes will become indistinct chromatin
- Cytokinesis takes place
- Cleavage furrow
Explain cytokinesis in animal cells
- Cleavage furrow formed because of contractile ring
- Division of the cytoplasm
Explain cytokinesis in plant cells
- Has a cell wall
- Division of cytoplasm
- Formation of cell plate which is made up of vesicles that contain cell wall components fused together
