Sexual reproduction requires chromosomal content to be halved in the sex cells to produce haploid gametes

  • The process by which haploid gametes are created is called meiosis (meiosis I is the reduction division)
  • Fusion of two haploid gametes creates a diploid zygote that can then grow and develop via mitotic division

If meiotic formation of haploid gametes did not precede fertilisation, chromosomal content would double every generation

  • Polyploidy is a condition whereby an organism has more than two complete sets of chromosomes in all cells (i.e. > diploid)
  • Polyploidy is far more common in plant species which lack separate sexes and are capable of self-pollination
  • Polyploidy is very rare in animal species due to the consequences of having extra allele copies of every gene

Kirby Genetics #2:  Sexual Reproduction via Meiosis or Mitosis

kirby two