Androgenesis (andro = male)

Androgenesis is the generation of a competent adult derived from enucleated eggs with only nuclei from sperm.

1) Eggs are enucleated by subjecting the nuclei to ultraviolet radiation or by a variety of other techniques.

2) The enucleated eggs are fertilised by a fertile sperm or with ICSI. This results in a haploid (one half the normal compliment of chromosomes) egg. Intracytoplasmic Sperm Injection allows the fertilisation of oocytes or enucleated eggs with sperm nuclei. This allows the use of oocytes of one species to be fertilised by the sperm of another or fertilisation with immotile or damaged sperm.

3) When the haploid egg first attempts to divide, cytokinensis (the splitting of the egg into two cells after the duplication of the nuclei) is prevented thus resulting in a diploid cell (a cell with the normal number of chromosomes).

4) This cell grows into a normal diploid animal (fish or frog).

Limitations

5) The derived animals are subject to the effects of inbreeding (Inbreeding Depression) as they are essentially the result of self fertilisation. However, genetic diversity may be re-established in subsequent generations by fertilisation with genetically diverse sperm.

6) Depending on whether the sex determining genes are found in the sperm or oocyte nuclei the animals may be female or male, or only male.