Final answer:
In cloning by somatic cell nuclear transfer, the DNA from an adult cell directs the development of an egg into a clone. A diploid nucleus from the adult donor replaces the egg's nucleus, and after stimulation to divide, the result is a genetically identical organism to the donor.
Step-by-step explanation:
In cloning by somatic cell nuclear transfer, the DNA from a adult cell directs the development of an egg into a clone of the organism that provided the DNA. In sexual reproduction, a haploid egg and sperm fuse to form a diploid zygote, containing genetic information necessary to produce a new individual. Cloning techniques take advantage of this by replacing the haploid nucleus of an egg cell with a diploid nucleus from an adult donor's body cell, resulting in a zygote genetically identical to the donor. This egg is then stimulated to divide, closely mirroring the natural developmental process.
For instance, Dolly the sheep was successfully cloned using a nucleus from an adult somatic cell. The nucleus was placed in an enucleated egg cell, which was then stimulated to divide and develop into an organism. Important to note is that all cells, whether somatic or gametes, contain the same genome, but the expressed genes differ during development.
It is significant that the cytoplasm of the egg plays a crucial role in early embryonic development, providing nutrients and organelles like mitochondria that are derived from the egg, not the sperm. This sets the groundwork for the cloned embryo's growth and development.