Which theory postulates that an organism is derived from materials originally present in the egg that eventually differentiate into adult structures during development?

Epigenesis theory suggests that the embryo arises from a single celled egg.

The epigenesis describes the morphogenesis as well as the process of development of an embryo from an egg. The epigenesis suggests that, the cells of egg continues to divide mitotically and later, these cells are specialised depending on its function. the process of specialisation is known as cell diferentiation. the morphogensis of an organism takes place through the expression of specific genes in different types of cells.

thymine. in rna, thymine is replace by uracil

it would lead to upper respiratory infections and pneumonia.