mitosis Flashcards
1
Q
when is mitosis necessary
A
- when daughter cells have to be genetically identical (growth, replacement, repair of tissues in multicellular organisms)
- asexual reproduction
2
Q
what happens before mitosis in interphase
A
- DNA replicated
- each DNA molecule is converted into 2 identical DNA molecules called chromatids
- chromatids are joined at the centromere
- DNA combines with histones (proteins) to form a dense complex called chromatin
3
Q
prophase
A
- chromatin fibres (complex made of proteins, RNA,DNA) coils, condenses to form chromosomes which take up stain to become visible under light microscopes
- nucleolus disappears
- nuclear membrane breaks down
- microtubules form spindle-shaped structures linking poles
- fibres forming spindle necessary to move chromosomes into correct positions
- centrioles(bundles of protein that form spindle) migrate to poles
- spindle fibres attach to centromeres and move chromosomes to centre
4
Q
metaphase
A
- chromosomes are moved by spindle fibres to form the metaphase plate in the centre
5
Q
anaphase
A
- centromeres holding the pairs of chromatids divide
- chromatids separated and pulled to opposite poles by shortening spindle fibres
- āVā shape due to being dragged through liquid cytosol
6
Q
telophase
A
- chromatids reached poles and are now called chromosomes
- 2 new sets of chromosomes assemble at each pole
- nuclear envelope reforms around them
- chromosomes uncoil, nucleolus is formed
- cytokinesis begins
7
Q
cytokinesis in animal cells
A
- cleavage furrow forms in middle of the cell
- cell surface membrane is pulled inwards by the cytoskeleton until it fuses in the middle
8
Q
cytokinesis in plant cells
A
- vesicles from Golgi apparatus assemble in the same place where the metaphase plate was formed
- vesicles fuse with each other and the cell surface membrane, dividing cell into 2
- new sections of cell wall form along sections of cell membrane
