Junk DNA
Many scientists have an evolutionary view of the genome and they prefer criteria based on whether DNA sequences are preserved by natural selection.
Haldane, and by Nobel laureate Hermann Muller, that only a small percentage of the human genome contains functional DNA elements (genes) that can be destroyed by mutation.
[10][11] (see Genetic load for more information) In 1966 Muller reviewed these predictions and concluded that the human genome could only contain about 30,000 genes based on the number of deleterious mutations that the species could tolerate.
This prompted a series of papers and letters describing transposons as selfish DNA that acted as a parasite in genomes and produced no fitness advantage for the organism.
[34][35][36][37][38] Opponents of junk DNA interpreted these results as evidence that most of the genome is functional and they developed several hypotheses advocating that transposon sequences could benefit the organism or the species.
[17] "A concept that is repugnant to us is that about half of the DNA of higher organisms is trivial or permanently inert (on an evolutionary timescale).
According to an article published in 2021 in American Scientist: Close to 99 percent of our genome has been historically classified as noncoding, useless "junk" DNA.
[28] In another publication from the same year Comings again discusses the term junk DNA with the clear understanding that it does not include non-coding regulatory sequences.
[48]Some of the criticisms have been strong: Revisionist claims that equate noncoding DNA with junk merely reveal that people who are allowed to exhibit their logorrhea in Nature and other glam journals are as ignorant as the worst young-earth creationists.
[55][1][56][57][58][2][46][59][5][45][9] Non-functional DNA is rare in bacterial genomes which typically have an extremely high gene density, with only a few percent being not protein-coding.
For instance, an analysis of 14,623 individuals identified 42,765 structural variants in the human genome of which 23.4% affected multiple genes (by deleting them or part of them).
[62] (3) Only a small fraction of the human genome is conserved, indicating that there is no strong (functional) selection pressure on these sequences, so they can rather freely mutate.
[66] Opponents of junk DNA argue that biochemical activity detects functional regions of the genome that are not identified by sequence conservation or purifying selection.
[67][8][68] According to some scientists, until a region in question has been shown to have additional features, beyond what is expected of the null hypothesis, it should provisionally be labelled as non-functional.
