Meiosis

Meiosis has Genetic variation Four daughter cells produced Parent cells are diploids but daughter cells are haploids Produces gametes

Two gametes fuse om fertilisation to produce new offspring New cells need 46 chromosomes Chromosome number must be halved to maintain diploidy Ensured by two meiotic divisions

Identical arms on the same chromosome

1) DNA replicates in parent cell during interphase 2) Nuclear envelope and nucleolus break down 3) Maternal and paternal chromosomes pair up at the centre of the cell ( Different to mitosis) 5) Two meiotic divisions 4) Crossing over and separation of sister homologous chromosomes (I) 5) Seperation of sister chromatids (I) 6) Results in two genetically different gametes produced

Crossing over, independent segregation, random fertilisation and mutation

1) Homologous pairs line up -> one into each cell 2) Line arrangements are random 3)Independent segregation arises as combination of maternal and paternal chromosomes within daughter cell is random

1) Homologous chromosomes line up 2) Non-sister chromatids overlap and entwine 3) Equivalent portions of chromatids exchanged and recombined due to tension breaking them off 4) Recombinant chromatids are formed 5) New genetic combinations of maternal and paternal alleles are produced

Points of contact between homologous chromosomes during crossing over there are usually multiple

Crossing over is more rare so if a question is showing the frequency of different type of the zygotes formed after meiosis the one with the phenotype that is less frequent is usually crossing over