A Twofer]. The topic was junk DNA. Jonathan M had posted an article on Uncommon Descent where he claimed that The Onion Test is an argument in favor of junk DNA [Thoughts on the “C-Value Enigma”, the “Onion Test” and “Junk DNA”].
I explained, as politely as I could (not), that the onion test was not an argument in support of junk DNA. It's a "test" for those who think they can explain the presence of large amounts of supposedly functional DNA that looks a lot like junk. The "test" is to apply your reasoning to the genomes of various onion species to see if it makes sense.
Do you think that the excess DNA protects against mutations? Then why do some onions need a lot more protection than humans?
Do you think that the extra DNA can be explained by alternative splicing? Why do some onion species need more alternative splicing than others?
Do you think that most of the extra DNA is required for regulating gene expression? Then why do onions need more sophisticated regulation than humans?
This ain't rocket science. The description of the Onion Test is pretty easy to understand—unless, of course, you are an IDiot.
Jonathan M has taken another shot at attacking the Onion Test. This time his article appears on the official blog of The Discovery Institure: Why the "Onion Test" Fails as an Argument for "Junk DNA". The title sort of gives it away, doesn't it? We're still dealing with an IDiot.
Briefly stated, the often cited "onion test" observes that onion cells have many times more DNA than human cells do. And since the onion is considered to be relatively simple as compared to us, this discrepancy -- it is argued -- can only be accounted for if the preponderance of its DNA is, in fact, junk or non-functional. Let's see whether the concept really holds any water.Let's go over this one more time. The Onion Test is a "test." (Look up the word "test" in the dictionary.) It's designed as a thought experiment to test a hypothesis about the possible function of large amounts of noncoding DNA. If you think you have an explanation for why most of the human genome has a function then you should explain how that accounts for the genomes of onions. Ryan Gregory knew that most so-called explanations look very silly when you try using them to account for genome size in onion species.
The Onion Test is not an argument in favor of junk DNA. It's a reality check on speculations about function.
Jonathan M still doesn't get it.
Are we surprised?