Mitosis and replication Flashcards
What must happen before a cell can divide?
- organelles must replicate
- DNA must replicate
- cell must grow
Why is it important that mitosis produces genetically identical copies of a parent cell?
- growth of new cells
- repair of damaged tissues
- asexual reproduction
What are the stages of the cell cycle?
Interphase: - G1 (cell growth, organelle synthesis and replication)
- Synthesis - DNA replication
- G2 - (growth and protein synthesis for replication)
Prophase
Metaphase
Anaphase
Telophase
Cell division (cytokinesis)
What happens during prophase?
- nuclear membrane and nucleolus disappears
- chromatin condenses into chromosomes - condense and stain darker
What happens during metaphase?
- centrioles begin to produce spindlefibres which attach to the centromere of chromosomes
- chromosomes arrange in the middle of the cell on the equator, held by centromeres
What happens during anaphase?
- spindlefibres attached to centromeres begin to contract and shorten
- as the spindlefibres shorten, the chromatids are separated and pulled to opposite sides of the cell (different poles)
- requires energy from ATP
What happens during telophase?
- spindlefibres disintegrate
- chromosomes disperse and become long and thin and the nuclear membrane reforms
- cell plate forms and membrane begins to cleave
What is the formula for mitotic index?
number of cells with visible chromosomes divided by total number of cells observed
How does a tumour develop?
- initially an early tumour is formed through uncontrolled cell division
- the tumour enlarges from the edges (has no capsule so can uncontrollably grow) and begins to develop blood vessels and lymphatic vessels
- ?
How do mutations affect the process of tumour growth?
- 2 genes called protoncogenes and tumour supressor genes
- if they are mutated the cell cycle cannot be controlled and this will lead to abnormal growth which causes tumours
- if both genes are mutated then the cancer will be more aggressive
how do prokaryotic cells replicate?
- replication of plasmids, circular DNA and ribosomes
- cell is ready to divide so replicated molecules attach to the membrane
- membrane grows which pulls molecules apart
- start of cell division - cell begins to cleave
- the cell splits into 2 separate daughter cells
how do viruses replicate?
- the virus attaches to a target cell eg. epithilial cells
- the cell engulfs the virus by endocytosis
- viral contents are released, viral RNA enters the nucleus where it is replicated by the viral RNA polymerase
- viral mRNA is used to make viral proteins
- new viral particles are made and released into the extracellular fluid. The cell, which is not killed in the process, continues to make new viruses
