Amplification in Differentiating and Differentiated Systems - Many experiments have been conducted which give merely indirect proof of DNA amplification, mainly based on the need of non mitotic DNA synthesis for specific growth and differentiation patterns, e.g. cell elongation and expansion.

Series of experiments on elongation have shown the need of an early DNA replication preferentially localized in chromocenters.

Another cell differentiation process wherein an important role for gene amplification has been suggested is xylem differentiation.

During the sequence of events leading to xylogenesis an extra replication of DNA sequences coding, at least in part, for ribosomal RNA has been reported.