People never mention the source of RNA or DNA in cells?

In a few words, viruses are infectious agents with either a DNA or RNA genome that absolutely need to parasite a host - without any restriction as to its nature (Eukarya, Archae or Bacteria) - to .... This is all the more intriguing since such functioning has never been observed in the modern cellular world. read more

In most mammalian cells, only 1% of the DNA sequence is copied into a functional RNA (mRNA). Only one part of the DNA is transcribed to produce nuclear RNA, and only a minor portion of the nuclear RNA survives the RNA processing steps. One of the most important stages in RNA processing isRNA splicing. In many genes, the DNA sequence coding for proteins, or "exons", may be interrupted by stretches of non-coding DNA, called "introns". read more