mitosis; ocr biology a level

mitosis

nuclear division

what is mitosis required for

asexual reproduction
repair
growth

the chromosomes are replicated into chromatids

interphase

how do chromosomes become chromatids

DNA combines with histones to from a dense complex called chromatin

what are the four stages of mitosis

prophase
metaphase
anaphase
telophase

what are chromatin fibres made up of

RNA and DNA

what happens in prophase

chromatin fibres coil and condense
the nucleolus disappears and the nuclear membrane begins to break down
protein microtubules form spindle-shaped structures linking the poles of the cell
two centrioles migrate to opposite poles of the cell

what happens in metaphase

the chromosomes are moved by the spindle fibres to form a plane in the centre of the cell at the metaphase plate

what happens in anaphase

the centromeres holding together the pair of chromatids divide. the chromatids are separated and pulled to opposite poles of the cell by shortening spindle fibres

what happens in telophase

the chromatids have reached the poles and are now chromosomes. the nuclear envelope reforms around them
cytokinesis begins

interphase

prophase

metaphase

anaphase

telophase