Cell Division - 16.2 Flashcards
How many cells does mitosis produce?
Two new cells
What are the three important functions of mitosis?
*Growth - organism can mature from single celled zygote
- Maintenance - cells replace worn out cells
- Repair - Cells regenerate damaged tissues
How are the three functions (growth, maintenance, repair) accomplished
Each daughter cell must have correct genetic information
What are the cellular events that must take place for daughter cells to be produced?
- Genetic material of one of the parents must be replicated
- The replicated chromatin must be condensed and organized in the nucleus
- One complete set of chromosomes must be divided into each of the two nuclei
- Cytoplasm must divide to produce two complete and functional daughter cells
When does DNA replication take place?
S phase of interphase
What is prophase?
When the chromatin condenses into tightly packed chromosomes.
What are the events that happen in prophase?
- Nuclear membrane breaks down - chromosome is released into the cytoplasm - nucleus disappears
- Centrioles move apart to opposite poles of the cell
- Network of spindle fibers forms between the centrioles
- Microtubules (hollow tubes of protein that facilitate movement of chromosomes within a cell).
- Spindle fibres lengthen with the addition of microtubule subunits (removal will cause them to shorten)
What is metaphase?
The spindle fiber guides the chromosomes to the equator or the centre line of the cell.
What are the events that happen in metaphase ?
- Spindle fires from opposite poles attach to the centromere of each chromosome
- attach in a way that one sister chromatid faces one pole while the other faces the opposite pole
- Each pair of sister chromatid is considered to be a single chromosome (as long as they are joined at centromere)
What is anaphase?
When the centromere splits apart and the sister chromatids separate from one another.
What are the events that happen in anaphase?
- The spindle fibre that link the centromeres to the poles of the cell shorten
- as they shorten, sister chromatids are pulled to opposite poles
- Other microtubules in the spindle apparatus lengthen and force the poles of the cell away from each other
- At the end of this phase - one complete diploid set of chromosomes has been gathered at each pole of the elongated cell
What happens in Telophase?
Telophase begins when chromatids have reached the opposite poles of the cell.
What are the events in telophase?
- The chromatids begin to unwind into longer less visible strands of chromatin
- Spindle fibre breaks down
- Nuclear membrane forms around each new set of chromosomes - nucleous forms within each nucleus
What process happens after mitosis?
Cytokenesis
What happens during cytokinesis in animal cells?
- Indentation form in the cell membrane along the equator
- Idenation deepens until the cell is pinched into two
