Telomeres and DNA degradation, simplified
I have recently come across the creationist’s “degradation of the DNA” argument. Some creationists claim that owing to the nature of our telomeres, DNA degrade over the generations, making evolution more than impossible. I spent some time researching this matter and came up with interesting results; I would like to share them with you all!
What are telomeres?
Telomeres are regions of repetitive DNA found at the ends of chromosomes. Due to the way that cells split, information at the chromosomes’ ends are lost. Telomeres are repeats of DNA, which ensures that information is not lost during the split.
The chromosome and its telomeres.
Telomeres shorten over time.
The next concept to grasp is that telomeres generally shorten over time. The creationists got this right (what a great surprise!). Telomeres shorten at every cell division (this also explains why cells age). But why do telomeres shorten? During division, the DNA’s two strands unwind, and two new strands come into match with the existing base pairs. This is done with the help of RNA, and RNA occupies a space at the end of the chromosomes. That occupied space is left untouched at the end of the process. After many divisions, one can see why telomeres would shorten, and when it runs out: wah-lah, DNA degradation!
Introducing the telomerase.
Telomerases are enzymes which extend the length of telomeres. There is a limited supply of these enzymes in older cells, therefore telomere shortening is somewhat inevitable, and the creationist’s claims still hold… But! Here’s the twist:
“Telomerase remains active in sperm and eggs, which are passed from one generation to the next. If reproductive cells did not have telomerase to maintain the length of their telomeres, any organism with such cells soon would go extinct.” - Lee Siegel, University of Utah
So consider again the replication of cells, this time with the advantage of the telomerase. Immediately the creationist’s argument falls into pieces.
We ought to love these telomerases, without which eukaryotes could not have easily evolved (prokaryotes - eg. bacteria - have circular chromosomes, so there are no chromosome ends for them to worry about). On a different note, telomerases are activated in cancer. Cancerous cells are, like other cells, subject to telomere shortening, however, if telomerases are activated, then they become immortal cells, so to speak. Perhaps the biggest key to curing cancer is to figure out how to deactivate these telomerases altogether!
Incidentally, this year’s Nobel Prize in Physiology or Medicine went to Blackburn, Greider and Szostak for the discovery of ‘how chromosomes are protected by telomeres and the enzyme telomerase’.
In summary, telomeres do shorten, but telomerases extend the telomeres during reproduction, therefore DNA’s do not degrade down the generations as the creationists claim. And if the creationist should like to use the telomerase as an example of intelligent design, remember that this troublesome, shortening telomere is already a blatant example of unintelligence. God bless.
I somehow found this website – and am somewhat interested in evolution.
I think I follow your argument – that children of the parent will have a full load of telomerases since sperm and eggs have a full set.
But in regard to evolution – it would seem that something like telomerases would only kindof evolve after the telomeres – right? So in the thousands / millions of years between when there were only telomeres but no telomerases – one could imagine that you’d be having trouble keeping information around?
Anyway – back to work.
Suggested reading (abstract only)
http://www.landesbioscience.com/curie/chapter/3541/
But here is a good full journal article (1998) to read:
http://www.uic.edu/labs/nakamura/pdf/4.pdf
It addresses your question of telomerase evolution.
Especially look at the section “Telomeres Lost: What happens in the absence of telomerase?” and “perspectives on the origin of telomerase”
Regards,
TANKS A LOT
I’m interested to know moving forward with this hypothesis on how it explains why through evolution this can ensure each successive mutation is a beneficial mutation and not a harmful mutation?
That was my understanding of the DNA degeneration argument, that over time as there is no design and no control; subsequent good mutations would need to be consecutively written over previous good mutations at the base level, and never be replaced by bad mutations. And if a bad mutation then wrote over a good mutation along that chain…start again. And since mutations carry through generations and can’t just be averaged over a total number of that species etc… Which one would think at such a low genetic level would create an immense number of random and unpredictable changes given the complexity of DNA. This large amount of mutation which wouldn’t be determined as beneficial or detrimental immediately would be continuously and very slowly degrading the quality of the DNA structure. Genetic illness etc…
And if we have evolved from less perfect DNA, why our DNA is now more perfect yet genetic illness and other factors have shown our DNA has reduced in quality ever so slightly over the years?
Additionally if you have knowledge on it, I would like to understand based on the premise that random evolution is randomly expedited based on environmental conditions; why animals living on the fringe of extreme conditions in our world today aren’t going through that ‘explosive’ evolution. And it would need to be explosive given the totally unimaginable number of possible random mutations needed to create a significant beneficial mutation creating a new species (following the process of a successful mutation each generation multiplied out)?
I understand these questions are posed in a somewhat negative fashion, but honestly I’m undecided and have asked them in the easiest way I see to answer
I don’t believe evolution either proves or disproves Christianity, or any other religion of the sort, as Genesis is written in such a fashion that old-earth and new-earth theories both hold; so a little irrelevant, just interesting for the sake of understanding!
Dear Mick. Many thanks for your comment. I don’t feel qualified to answer your DNA-specific question partly because I don’t see why evolution should have to “ensure” beneficial mutation over harmful mutations which is the premise of your argument. The very nature of DNA replication seems contest the idea that “good mutations would need to be consecutively written over previous good mutations at the base level”, but perhaps I am misconstruing your question. Also, is it not the case with natural selection that favourable traits are transmitted and unfavourable ones generally eliminated? Please could you also clarify what constitutes “more perfect” DNA as it seems to me progressive “perfection” is a Spencerian rather than Darwinian idea. In any case I suggest you have a look at the following link as you may find it slightly useful: http://www.nature.com/scitable/topicpage/dna-replication-and-causes-of-mutation-409
As per your second question it must be noted that when you say “extreme conditions” you are simply referring to what is extreme to human beings. Perhaps a polar bear may find living in the desert extreme, likewise a camel in the North Pole. Evolution is simply adaptation to certain environmental conditions therefore I am unsure why being in so-called extreme conditions should necessitate “explosive” evolution. Perhaps if you could kindly clarify these points I may be able to address your questions in a somewhat more satisfactory way.
Best wishes
Cheers Tim, i’ll see if I can elaborate a bit.
I wasn’t suggesting that evolution should have to ensure beneficial mutation, but rather it seems to be in complete agreement that overall less good mutations occur then bad mutations.
Now mutations aren’t so much as one day we give birth and your baby has a cute little pair of wings, as amazingly cool as that would be
It’s thousands upon many millions of consecutive changes which slowly build upon one another to form that appendage.
And those millions of mutations which begin to form wings would have to build on one another in a positive fashion, and carry forth through each generation successfully. Moreso it would provide no significant advantage to cater for natural selection until enough mutations had successfully built on one another for it to allow the ‘leap forward’ needed to survive ahead of the rest of its counterparts.
For example Ape DNA and Human DNA can have almost 20 million base comparisons made between the two and it still only equates to roughly 1% of the genome. And when we are between 98-95% different we could have up to 100 million base variances. Which to build upon in successful generations to create modern man from primate, it begins to take shape how long this would have actually needed to occur (just as one example).
And during these millions of successive mutations, since intelligent design doesn’t exist, the DNA would have no concept of if its going down the right path or not. So if anywhere along that lengthy chain of offspring something mutates incorrectly, it could just as quickly make the slowly developing new appendage unstable/unusable and reset that entire chain of mutation before it ever reached maturity.
Not to mention since it would take so much time for a mutation to change a species enough to then cause it to survive in place of the others dying out, it would be expected that during that time there would be an exponential level of other mutations all occurring in parallel which are all in various states of development.
This is where I find it gets tricky, as when math is applied to this, very very quickly it becomes apparent that;
1. If evolution is very gradual, there has not been anywhere near enough time since the conception of the universe for it to explain the sheer amount of diversity with the minuscule level of transition we can see in the entire population of life on the planet today.
2. If evolution is sped up depending on environment we would see great deals of continual evolution now in fringe conditions such as volcanos, deserts, polar regions etc… good and bad, transitional etc… but we don’t.
On top of this my comment also related to the quality of DNA, i’ll spend less time of this as its secondary and I don’t know that much about it (thus me asking, keen to know more
. My understanding was our DNA now is less stable then it was in the past, resulting in more bad mutations, more birth defects, higher intolerance to interbreeding within families etc… and if evolution was the cause of all life, that would not occur. Most of the available data (as what I read in your link) relates to DNA degeneration during someone’s lifetime rather then slow degeneration causing instability through successive generations.
Hope that helped to clarify my initial post.
Thank you Mick for clarifying these points.
Again I try but I don’t see a real issue here. I am in agreement with many of your premises but forgive me for remaining sceptical that they necessarily lead to your noted conclusions:
“1. If evolution is very gradual, there has not been anywhere near enough time since the conception of the universe for it to explain the sheer amount of diversity with the minuscule level of transition we can see in the entire population of life on the planet today.”
>> Yet evidence seems to suggest otherwise??
“2. If evolution is sped up depending on environment we would see great deals of continual evolution now in fringe conditions such as volcanos, deserts, polar regions etc… good and bad, transitional etc… but we don’t.”
>> I’m not sure I agree with this (for the reasons previously given — revisit my previous response), though I think **varying** environmental conditions might have an effect on evolutionary speed. The rate of evolution can also depend on the lifespan of a generation ie. more reiterations to work with.
“if anywhere along that lengthy chain of offspring something mutates incorrectly, it could just as quickly make the slowly developing new appendage unstable/unusable and reset that entire chain of mutation before it ever reached maturity.”
>> How so? How is the fate of one whole “chain(?)” of a species dependent on ONE offspring who may or may not mutate “correctly”????
“Moreso it would provide no significant advantage to cater for natural selection until enough mutations had successfully built on one another for it to allow the ‘leap forward’ needed to survive ahead of the rest of its counterparts”
>> The story of eye evolution would render this argument obsolete, http://learn.genetics.utah.edu/content/variation/eye/ (and I think it was Dawkins who said — and I paraphrase — half a wing or even 10% of a wing is still better than having no wings at all.) Also it may serve you well to recall Behe’s irreducible mousetrap argument, wherein he neglects the possibility that independent parts of the mousetrap may have evolved to serve entirely different functions.
I hope I have been of some assistance at all, but may I remind you that since I am no expert on evolution it will be wise that you read my responses some degree of vigilance!