>> The non-coding sequences are common to all living organisms on Earth, from moulds to fish to humans. <<
Not possible. Human DNA, which goes 97% unread by mDNA, is hundreds of times more complex than some bacterial DNA. I think what the author means to say is the much less fantastic statement, "all organisms have some non-coding sequences in their DNA."
Boring Sci-fi people. The cooler explanation is that the "junk DNA" is a design for some future race of mankind.
THE REAL REASON FOR JUNK DNA:
Each gene produces one protein. So, if cellular transcription occurs at a fairly steady, environmentally controlled rate, how do organisms make more or less of a given protein?
They make COPIES of the DNA. DNA doesn't actually get used to produce protein, directly. It serves as the template for mRNA. The more protein needed, the more mRNA is produced.
Redundant copies of DNA also have the same benefit, but gene B is a copy of gene A, either gene A or gene B can be destroyed, without the likelihood of the organism being impaired. Also, viruses insert their genes into DNA as a way of replicating themselves. Typically they pick up portions of human DNA when they do this. This is actually quite common, and it is how gene therapy typically is done.
(This info was what was believed as of my college education, which was over a decade ago.)
No. The author meant what he wrote. But he probably overstated it in terms of some organisms.
However, even some microbes etc. are surprisingly complex in their DNA.
IIRC, I read a thread on FR recently that some very small organisms have DNA MORE COMPLEX than humans.