1. Genetic load
You can't understand the junk DNA debate unless you've read Michael Lynch's book The Origins of Genome Architecture. That means you have to understand modern population genetics and the role of random genetic drift in the evolution of genomes. There's no evidence in Parrington's book that he has read The Origins of Genome Architecture and no evidence that he understands modern evolutionary theory. The only evolution he talks about is natural selection (Chapter 1).
Here's an example where he demonstrates adaptationist thinking and the fact that he hasn't read Lynch's book ...
At first glance, the existence of junk DNA seems to pose another problem for Crick's central dogma. If information flows in a one-way direction from DNA to RNA to protein, then there would appear to be no function for such noncoding DNA. But if 'junk DNA' really is useless, then isn't it incredibly wasteful to carry it around in our genome? After all, the reproduction of the genome that takes place during each cell division uses valuable cellular energy. And there is also the issue of packaging the approximately 3 billion base pairs of the human genome into the tiny cell nucleus. So surely natural selection would favor a situation where both genomic energy requirements and packaging needs are reduced fiftyfold?1Nobody who understands modern evolutionary theory would ask such a question. They would have read all the published work on the issue and they would know about the limits of natural selection and why species can't necessarily get rid of junk DNA even if it seems harmful.
People like that would also understand the central dogma of molecular biology.
1. He goes on to propose a solution to this adaptationist paradox. Apparently, most of our genome consists of parasites (transposons), an idea he mistakenly attributes to Richard Dawkins' concept of The Selfish Gene. Parrington seems to have forgotten that most of the sequence of active transposons consists of protein-coding genes so it doesn't work very well as an explanation for excess noncoding DNA.