Mitosis Flashcards
Why does mitosis occur
Mitosis occurs because cells need to be produced for growth and repair of tissues, so the cells must divide as cells arise from pre-existing cells
Describe what is produced after mitosis
2 genetically identical daughter cells
Why is it important that the cells produced in mitosis are identical
So they have the same structure and function as the other cells, to replace the damaged cells
Before mitosis, what genetic material is present in the cell
Chromatin
Describe what is meant by chromatin
Long, thin threads of DNA
Describe what happens during interphase
DNA replicates, and the ell synthesises a lot of ATP
What are each ‘leg’ of a chromosome called
Chromatids
Why does a chromosome have 2 chromatids
DNA has replicated
Describe what is meant by sister chromatids
Chromatids that contain identical genetic material
What holds together the 2 chromatids in a chromosome
The centromere
What does the centromere do during mitosis. Explain why
- The centromere wll divide, allowing the chromatids to be pulled apart into separate cells
- This ensures hat each cell gets an identical copy of DNA
What happens to the separated chromatids at the end of mitosis
The separated chromatids become longer and thinner again, where each new cell has an identical copy of DNA
Describe what happens to the DNA during mitosis to ensure that both cells produced are identical
- The DNA replicates during interphase prior to cell division
- The DNA condenses becoming shorter and thicker
- Chromosomes consisting of two identical chromatids held together by a centromere are formed
- The centromere divides and the two chromatids are pulled apart
- The chromatids becomes longer and thinner
What are 4 stages of mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Describe what happens during Prophase
- The nuclear envelope breaks down
- The chromosomes condense
- The spindle fibres are formed by organelles called centrioles, which move to opposite poles (ends) of the cell
Describe what happens during metaphase
- The chromosomes align in the middle of the cell
- Spindle firbres attach to the centromere of each chromosome
Describe what happens during Anaphase
- The centromeres divide
- The spindle fibres contract (which requires energy from ATP)
- The chromatids separate and are pulled to opposite poles
Describe what happens during Telophase
- The spindle fibres disintergrate
- The nuclear envelope begins to reform
- The chromosomes become longer and thinner once more
Describe birary fission in bacteria (3)
- Circular DNA replicates
- Plasmids replicate
- Cytoplasm divides to produce daughter cells
Suggest and explain how two environmental variables could be changed to increase the growth rate of these cells.
- Increase concentration of glucose
- This increases the rate of respiration
- Increase the temperature
- This increases enzyme activity
