Natural Clones in Animals

How can natural cloning occur?

- Embryo splitting

- Fragmentation

- Budding

- Parthenogenesis

What is budding?

The growth of a new animal out of the side of the original animal by mitosis

What is parthenogenesis?

A natural form of asexual reproduction in which growth and development of embryo clones occur without fertilisation by a male gamete

What is fragmentation?

It involves the breaking up of the original animal into small parts, each of which can then grow into a whole animal as seen in some corals, sea anemones and starfish.

Monozygotic Twins Process

1. An egg is fertilised by a sperm as in a singleton birth

2. This forms a zygote

3. The single zygote undergoes a few cell cycles (mitotic divisions) to become an embryo. This is why identical twins are referred to as monozygotic

4. At the embryo stage, the embryo splitting occurs.

5. Two embryos that form are identical, with the same genotype and develop in utero together

6. The result is the birth of identical offspring, always of the same gender, with identical phenotype

Why are non identical twins not considered twins?

Because non-identical twins are formed from separate eggs and sperm, they are not considered clones

Arguments for Artificial Plant Cloning

Desirable genetic characteristics always pass on to clones (doesn't always happen when plants reproduce sexually)

It produces lots of plants quickly, compared to the time it would take to grow them from seeds

Used to reproduce seedless fruit/plants

Propagation can be done at any time of the year

All the plants produced will be uniform

Arguments against Artificial Plant Cloning

Undesirable characteristics passed on

Low genetic diversity, so disease can easily wipe them out

Contamination by microorganisms during tissue culture can be disastrous and result in complete loss of the plants being cultured