Mitosis Flashcards
what are the three stages in the cell cycle?
interphase [ G1, S G2] , nuclear division [mitosis or meiosis] and cytokinesis.
what happens in prophase?
The chromosomes condense
The centrioles duplicate
The centriole pairs move towards each pole
The spindle begins to form
what happens in metaphase?
The nuclear envelope disappears
The centriole pairs are at the poles
The spindle is completely formed
The chromosomes continue to condense
The microtubules of the spindle attach to the centromeres of the chromosomes
The microtubules pull on the centromeres, arranging them on the equator
what happens in anaphase?
The links between sister chromatids break
The centromeres of sister chromatids move apart, pulled by the microtubules of the spindle
what happens in telophase?
Sister chromatids (now effectively separate chromosomes) reach opposite poles
what happens in cytokinesis?
The chromosomes decondense
Nuclear envelopes appear around the chromosomes at each pole
The spindle disappears
The cell divides into two cells, by infolding of the plasma membrane in animal cells, or by formation of a new cell wall and plasma membrane in plants
what can mitosis lead to sometimes?
Sometimes these control mechanisms break down and this means that the resulting cell may be able to divide repeatedly in an uncontrolled way. These are cancer cells, and given a supply of nutrients they can grow into a tumour.
describe what happens in binary fission?
Bacterial cells divide by binary fission
* replication of the circular DNA and of plasmids
* division of the cytoplasm to produce two daughter
cells, each with a single copy of the circular DNA
and a variable number of copies of plasmids
what issues with non living viruses?
Being non-living, viruses do not undergo cell
division Following injection of their nucleic acid, the infected host cell replicates the virus particles
