Meiosis & Fertilisation in Sexual Reproduction
- Meiosis is a form of nuclear division that results in the production of haploid cells from diploid cells
- It produces gametes in plants and animals that are used in sexual reproduction
- It takes place in two successive divisions: meiosis I and meiosis II
- More information about meiosis can be found here
- During meiosis, specific mechanisms occur to lead to genetic variation within the resulting gametes, this breaks up parental combinations of alleles derived from the mother and father chromosomes
- Crossing over - the process by which non-sister chromatids exchange alleles during meiosis I
- Independent assortment - the production of different combinations of alleles in daughter cells due to the random alignment of homologous pairs of chromosomes during meiosis I
- Random fertilisation - there are millions of combinations of sperm and egg cells and the fusion of these sperm and egg cell
- Within each division there are four stages; prophase, metaphase, anaphase and telophase
- Meiosis occurs:
- In the testes of male animals and the ovaries of female animals
- In the anthers and ovaries of flowering plants
- Meiosis leads to the production of the following haploid gametes:
- Spermatozoa, or sperm cells, in male animals, ova (singular ovum) in female animals
- Male plant gametes are carried in pollen grains and female plants gametes are held in the ovules within the plant ovary
- The fusion of gametes during fertilisation produces new combinations of alleles leading to genetic variation