Meiosis and genetic variation

• Alleles are one of the different forms of a gene
• Genes are base sequences of DNA that codes for the amino acid sequence of a polypeptide or functional RNA
• During the first meiotic division, homologous chromosomes pair up along the equator with random arrangement
• The maternal and paternal chromosomes are then reshuffled in any combination before being separated so that one chromosome of each homologous pair goes to each daughter cell
• Importance of chromosome segregation

  • produces genetically different haploid daughter cells
  • halves chromosome number to ensure it remains constant from one generation to another
  • diploid number is restored during fertilisation
• Number of possible chromosome combinations in a gamete due to independent segregation = 2 to the power of n
• Number of possible chromosome combinations in a zygote due to random fertilisation = (2 to the power of n) squared