MEIOSIS: DIVISION OF A PARENT CELL THAT PRODUCES
GENETICALLY DIFFERENT HAPLOID CELLS
each chromosome duplicates to become double stranded (like in mitosis)
each strand is called a chromatid
each chromosome becomes thicker, shorter and more visible. then chromatids are then joined at the centromere.
the nuclear envelope disappears
spindle fibres spread out from each end of the cell and attach to the centromere of each chromosome
similar* chromosomes then pair up in the centre of the cell
*the scientific word homologous can be used
Small parts of the homologous chromosomes cross over
this exchage of genetic material increases variation (eventually creating the different haploid cells)
the spindle fibres contract, seperating the homologous pair into opposite sides of the cell, which begins to divide
each chromosome is still formed of two chromatids
a new nuclear envelope forms around each set of chromosomes and the cell finishes dividing
each cell only has 46 chromosomes
The 2nd part of meiosis begins with the chromosomes condensing again and the nuclear envelopes disapearing
spindle fibres spread out at right angles and attach to the chromosomes.
the fibres contract, seperating the two chromatids in each chromosome. Each cell divides in two.
a new nuclear envelope forms around each set of chromosomes.
each cell contains 23 chromosomes and each chromosome is genetically different.