Thursday, December 13, 2012

Junk DNA, and Junk Creationism

(Heads up Feb. 24, 2013: There is a new paper "On the immortality of television sets: “function” in the human genome according to the evolution-free gospel of ENCODE," published in the "Genome Biology and Evolution" journal that does a total debunking of the absurd claims made by the ENCODE project).

The creationists, particularly the intelligent design breed, have been shouting that discovering some functions in "junk" DNA somehow proved their fantasy is correct. Discotute fellow Jon Wells even wrote a book about it, "The Myth Of Junk DNA."

Soon after the discovery of how DNA stored sequences used to replicate proteins there began a bidding war for research funds to specify the DNA sequences and identify their function. In the battle, non-coding sections were called "junk DNA" since there was no obvious function that could be intuitively connected with a particular gene. A protein coding sequence clearly had a function, even if what the protein did was unknown at the time. Since building a sequence data base was then extremely expensive (and boring), the argument against deciphering non-translated "Junk DNA" won out. But, the possible functionality of "Junk DNA" was raised in the late 1970s. The argument was simple: there was an evolutionary cost to making copies of useless DNA. Since this cost was being paid, the "Junk" must have a function. The human genome project was conceived after the discovery of polymerase chain reaction (PCR) in 1983. Many researchers were still objecting to spending scarce research money on non-coding sequences as late as 1989.

Some likely functions of this "junk" were discovered by geneticists in the late 1980s, reaching journal publications by the early 1990s. The development of automated sequencing machines around 2000 finally eliminated the last objections to sequencing "junk."

AD Riggs (1990) “Marsupials and Mechanisms of X-Chromosome Inactivation”.
Australian Journal of Zoology 37(3) 419 – 441 (Suggested that "junk DNA" would not be preserved without some function, identified control functions specifically as promoters of spreading).

J Brosius and S J Gould (1992) “On "genomenclature": a comprehensive (and respectful) taxonomy for pseudogenes and other "junk DNA"” PNAS November 15, vol. 89 no. 22 10706-10710 (They propose that “junk DNA” is evolutionarily significant by providing raw material for future functions, is implicitly the source for current gene functions, and preserves the evolutionary history of organisms. Received 1991).

Emile Zuckerkandl, 1992, “Revisiting junk DNA” Journal of Molecular Evolution Volume 34, Number 3 / March, 1992 (Received 1991) (Suggested that "junk DNA" would not be preserved without some function, speculated that there were control functions).

What did the creationists have? ... The best they can do is a 1998 article by William Dembski. In an article for the Christian magazine “First Things,” he noted the discovery of functionality by scientists (not by creationists) in portions of the human genome that had been considered as uninteresting “junk DNA” by many. Specifically, Dembski quotes Bodnar et al’s 1997 abstract from, “Deciphering the Language of the Genome.” To a competent reader, Dembski is defending creationism’s position from scientific advances by attempting to co-opt them.

Bodnar, JW, J Killian, M Nagle, S Ramchandani (1997) “Deciphering the Language of the Genome.” Journal of Theoretical Biology Vol 189, Issue 2, 21 November 1997 Pages 183-193).

Dembski, William A. (1998) “Science and Design” First Things 86 (October 1998): 21-27.

The ENCODE project began releasing reports with 30 articles published in the first week of September this year. They generated a great deal of excitement, and controversy. The first highly controversial topic was how they chose to define "functional" for DNA sequences. Basically, any segment of DNA that was transcribed by RNA was anointed as "functional." The directors of the project are already walking back from that claim. They weakly explained that the "public" might have been confused. Days later, a key project leader, Ewan Birney, Ph.D., was trying to justify using "80% functionality" in his press releases. His answer was to redefine "functional." In practical terms, "functional" became anything they could find that could bind somewhere. For what Birney admitted most people think of as "functional," the percentage falls hard to ~20%.

Here is a portion of his self commentary;.

Q. Ok, fair enough. But are you most comfortable with the 10% to 20% figure for the hard-core functional bases? Why emphasize the 80% figure in the abstract and press release?
A. (Sigh.) Indeed. Originally I pushed for using an “80% overall” figure and a “20% conservative floor” figure, since the 20% was extrapolated from the sampling. But putting two percentage-based numbers in the same breath/paragraph is asking a lot of your listener/reader – they need to understand why there is such a big difference between the two numbers, and that takes perhaps more explaining than most people have the patience for. We had to decide on a percentage, because that is easier to visualize, and we choose 80% because (a) it is inclusive of all the ENCODE experiments (and we did not want to leave any of the sub-projects out) and (b) 80% best coveys the difference between a genome made mostly of dead wood and one that is alive with activity. We refer also to “4 million switches”, and that represents the bound motifs and footprints.

We use the bigger number because it brings home the impact of this work to a much wider audience. But we are in fact using an accurate, well-defined figure when we say that 80% of the genome has specific biological activity. ... ughts.html

The only thing holding back "the progress of genomic research" has been lack of money, and the religious-right blocking stem cell research.

1 comment:

Anonymous said...

Gary, Great summary here of the ENCODE / junk DNA tempest. You nailed the key issues. FYI I wrote up a much longer version, quoting and debunking a number of specific ID claims - -

Also, thanks again for unearthing in an earlier Stones n' Bones post the M Luther passage used by Nazis -- I finally got around to citing it in an add-on to my "Was Darwin an Atheist?" article.
Happy holidays, Scott