3.21 understand that division of a cell by meiosis produces four cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametes

3.21 •sexual reproduction produces genetically different cells

                  •the father and the mother produce gametes

                  •gametes are haploid - they have half the number of chromosomes in a normal cell (23)

                  •at fertilisation, a male gamete fuses with a female gamete to form a zygote 

                  •the zygote then divides by mitosis and becomes an embryo, inheriting features from both parents

                  •random fertilisation of gametes means genetic differences 

                  •1st Division meiosis only happens in reproductive organs

                            •1. it duplicates it’s DNA, now having two identical arms 

                            •2. in this first division, they line up parallel in the centre

                            •3. the pairs are pulled apart 

                            •4. each new cell will have a mixture of the parents’ chromosomes 

                  •2nd Division 

                            •1. the chromosomes line up again in the centre - the arms are pulled apart, like mitosis

                            •2. four haploid genetically different gametes are made, each with one set of chromosomes