I read a book in 1973 and I've been looking for the name since. The book is in English and is adult sci-fi.
It opens with a young boy sitting at his desk watching words appear on a sheet of paper in front of him. It is from his uncle who has been cloned down to the size of a dust mote and he is dragging his body through a blob of ink to write his nephew a message. Clones are no longer accepted in society, so people no longer want them around. It ends with the boy, his uncle, and a girl floating off into space to explore their new world.
The uncle is a scientist and has been working on a cloning project and has been discovered by the government and is now on the run. He reaches out to the nephew for help. The nephew becomes involved and ends up being cloned twice. Once regular size and then dust mote size. People have grown suspect of clones wanting rights and freedoms. The government is after anyone helping clones or cloning.