before the cell divides - it duplicates the genetic information forming two armed chromosomes
first division = chromosomes line up in centre of cell
pairs are pulled apart so each new cell has one copy of each chromosome. both mother and father chromosomes go into each new cell
second divison = chromosomes line up and the arms of the chromosomes are pulled apart again
4 gametes are formed with a single set of chromosomes - genetically different
what happens to the gametes at fertilisation?
they join to restore the normal number of chromosomes. the new cells divides by mitosis. the number of cells increases. as the embryo develops cells differentiate.
