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The Complex Truth About ‘Junk DNA’

quantamagazine.org

11–20 of 63 posts

Re: The Complex Truth About ‘Junk DNA’

#11
post #4
post #2

Paragraph 4: “Slowly, slowly, slowly, the terminology of ‘junk DNA’ [has] started to die,” Rest of the article: continues to use the term "Junk DNA".

I think more than any other group, programmers can understand the gut reaction of calling code that they don't understand "junk".

Normally it means "poor quality" though. I think "junk DNA" is more analogous to "dead code". Not all code labeled "dead" is actually unreachable/unused.

Re: The Complex Truth About ‘Junk DNA’

#12
post #9
post #7

Earlier quoted context omitted.

Everyone doing biology professionally already knows the non-coding DNA has function. It’s only logical since we know that resource-intensive mechanisms don’t survive the evolutionary pressure if there’s no benefit for them to exist. So it’d be wasteful to replicate 98% of DNA if it’s not functional. Keep in mind it’s not only replicated, there’s error-correction as well.

it's wasteful to replicate non-functional DNA, yet there are organisms whose genomes are 10X-100X larger than any others (literally ten copies of a genome), and they do just fine ( https://en.wikipedia.org/wiki/Paris_japonica ). The cost of DNA replication isn't that strong a functional selection afaict.

Sounds like "non-functional DNA" might in fact have a function, hm?

Re: The Complex Truth About ‘Junk DNA’

#13
post #12
post #9

Earlier quoted context omitted.

it's wasteful to replicate non-functional DNA, yet there are organisms whose genomes are 10X-100X larger than any others (literally ten copies of a genome), and they do just fine ( https://en.wikipedia.org/wiki/Paris_japonica ). The cost of DNA replication isn't that strong a functional selection afaict.

Sounds like "non-functional DNA" might in fact have a function, hm?

Probably not in the context of the example I gave; that's more likely to just be a totally random genome duplication which will eventually be functionally selected away.

Re: The Complex Truth About ‘Junk DNA’

#14
post #9
post #7

Earlier quoted context omitted.

Everyone doing biology professionally already knows the non-coding DNA has function. It’s only logical since we know that resource-intensive mechanisms don’t survive the evolutionary pressure if there’s no benefit for them to exist. So it’d be wasteful to replicate 98% of DNA if it’s not functional. Keep in mind it’s not only replicated, there’s error-correction as well.

it's wasteful to replicate non-functional DNA, yet there are organisms whose genomes are 10X-100X larger than any others (literally ten copies of a genome), and they do just fine ( https://en.wikipedia.org/wiki/Paris_japonica ). The cost of DNA replication isn't that strong a functional selection afaict.

You're conflating the size of a genome with the amount of DNA that is non-functional.

Re: The Complex Truth About ‘Junk DNA’

#15
post #5

Most genetic variants associated with common diseases fall in non-coding DNA areas, previously thought to be junk DNA. Many of these non-coding areas are actually enhancer elements. These elements produce enhancer RNA, previously thought to be noise, and regulate distant genes thanks to chromosome conformation. Chromosome conformation means DNA folds in complex 3D patterns. The interplay between chromosome conformati…

For starters, junk DNA is a fuzzy term. I would never include regulatory regions or introns in junk DNA, just non-coding. To me, junk are tranposons and friends, or pseudogenes: they rarely have any purpose, and sometime they cause troubles.

Re: The Complex Truth About ‘Junk DNA’

#16
Since I learned of this so-called Junk DNA, I assumed that one function of it might be to dilute the density of critical DNA sequences.

In other words, if every base pair matters, then DNA damage from, say, ionizing radiation is more likely to be a problem than if only 1/100 base pairs matter.

Re: The Complex Truth About ‘Junk DNA’

#17
post #10
post #2

Paragraph 4: “Slowly, slowly, slowly, the terminology of ‘junk DNA’ [has] started to die,” Rest of the article: continues to use the term "Junk DNA".

Introduction: Introduces term. Early text: Details evidence that term is misguided. Late text: Continues to use early term so as to provide a consistent interface to readers. Might use 'scare quotes' if term is particularly egregious but still conserves familiarity of terminology.

What would you have them do instead? Naming stuff is hard. The authors get their point across quite nicely without also trying to coin more terminology.

Re: The Complex Truth About ‘Junk DNA’

#18
post #9
post #7

Earlier quoted context omitted.

Everyone doing biology professionally already knows the non-coding DNA has function. It’s only logical since we know that resource-intensive mechanisms don’t survive the evolutionary pressure if there’s no benefit for them to exist. So it’d be wasteful to replicate 98% of DNA if it’s not functional. Keep in mind it’s not only replicated, there’s error-correction as well.

it's wasteful to replicate non-functional DNA, yet there are organisms whose genomes are 10X-100X larger than any others (literally ten copies of a genome), and they do just fine ( https://en.wikipedia.org/wiki/Paris_japonica ). The cost of DNA replication isn't that strong a functional selection afaict.

And yet we probably don't know why they have so many copies. Maybe it's a crude method of regulating the ratio of activation on genes. If a few genes are either on or off, and you want to have ratios other than 1:0 1:1 or 0:1, maybe independently activating N of the M copies can achieve that. Just speculating as to how multiple copies might be useful.

You can't prove that they are "extra copies" until you understand pretty much everything about them and their interactions with everything else.

Re: The Complex Truth About ‘Junk DNA’

#19
post #5

Most genetic variants associated with common diseases fall in non-coding DNA areas, previously thought to be junk DNA. Many of these non-coding areas are actually enhancer elements. These elements produce enhancer RNA, previously thought to be noise, and regulate distant genes thanks to chromosome conformation. Chromosome conformation means DNA folds in complex 3D patterns. The interplay between chromosome conformati…

I remember talking to my colleagues about 15 years ago about trying to do research on some noncoding polymorphisms and was ridiculed. The basic response was something along the lines of "those are noncoding, why would you look at those?" as if I was an idiot who didn't understand current genetics.

It's been long ago enough that I don't remember all the details, but my perspective was that it was naive and arrogant to assume we had a good handle on everything about DNA, especially then as it was all new, and there was evidence then that a lot of the noncoding DNA had function.

Dogmatic attitudes are surprisingly prevalent in academics. There's definitely a weird hubris accompanying published findings that goes something like peer reviewed -> established fact as if the point of academics isn't to understand things but to score points like on a test. Some skepticism about certain things seems warranted but other times there's really nothing but overly simplistic models that were really never evaluated to begin with. I wish there was more awareness of the topography of uncertainty in research findings.

Re: The Complex Truth About ‘Junk DNA’

#20
post #14
post #9

Earlier quoted context omitted.

it's wasteful to replicate non-functional DNA, yet there are organisms whose genomes are 10X-100X larger than any others (literally ten copies of a genome), and they do just fine ( https://en.wikipedia.org/wiki/Paris_japonica ). The cost of DNA replication isn't that strong a functional selection afaict.

You're conflating the size of a genome with the amount of DNA that is non-functional.

I'm not conflating anything. Those details are scientifically conflated (IE, they are functionally related) in a very interesting way. For exmaple, new genes probably arise from gene or genome duplications.
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