Question

In cloning, which of the following is formed?

• A. Somatic nucleus is inserted into cytoplasm of fertilized egg.
• B. Ova are fertilized outside artificially.
• C. Other specialized cells are made to embryogenic development.
• D. Zygote is fused with somatic cells.

Answer 1

Answer: (C)

Other specialized cells are made to embryogenic development.

Normal mammalian embryonic development results from selective expression of some genes and repression of others. Tissue differentiation depends upon several types of epigenetic modifications of DNA structure and spatial organization that selectively turn genes on and off. The chromosomal DNAs of egg and sperm cells are modified during their maturation, so that at fertilization, both sets of DNA are ready for the complex pattern of gene expression required for normal embryonic development. In order for the DNA of a differentiated adult cell to direct embryonic development in cloning, it must be epigenetically reprogrammed. If the extent of epigenetic reprogramming varies from one cloning event to the next, the protein expression pattern and thus the biological properties of cloned stem cell preparations may also vary.

Therefore, the correct answer is option C.