Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 86 (8943 total)
39 online now:
DrJones*, kjsimons, PaulK, PurpleYouko, vimesey (5 members, 34 visitors)
Newest Member: LaLa dawn
Post Volume: Total: 863,957 Year: 18,993/19,786 Month: 1,413/1,705 Week: 219/446 Day: 17/98 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Genetic load: can someone explain?
slevesque
Member (Idle past 2931 days)
Posts: 1456
Joined: 05-14-2009


(1)
Message 31 of 53 (535810)
11-18-2009 4:24 AM
Reply to: Message 29 by Phydeaux
11-18-2009 2:39 AM


Re: Epistasis and fitness
Yeah I read his book. And well I do remember the part you are citing implicitly about his opinion of population geneticists.

But I do remember that recently he peer-reviewed an article about population genetics (specifically selection cost), the other peer-reviewers (they were 4 or 5 in total) were Crow, Kondrashov and one or two others.

So well I would think that he is considered knowledgeable enough to peer-review papers on the subject, than he probably is enough to write on it.


This message is a reply to:
 Message 29 by Phydeaux, posted 11-18-2009 2:39 AM Phydeaux has responded

Replies to this message:
 Message 33 by Phydeaux, posted 11-18-2009 9:39 AM slevesque has not yet responded

  
Phydeaux
Junior Member (Idle past 3493 days)
Posts: 13
Joined: 11-17-2009


Message 32 of 53 (535831)
11-18-2009 9:25 AM
Reply to: Message 30 by PaulK
11-18-2009 3:26 AM


Re: Deleterious mutations
quote:
Obviously the human population is not "essentially zero", so humans must have been around for less than 300 generations, right ?

That would fit quite happily with a timescale of 6000 years, but not with an Old Earth timescale (which cannot be much less than 200,000 years).


I believe that is just with Crow's data on 1-2% per generation. I know Sanford doesn't think it will be 300 generations from now though. Even in chapter 10 he says that 300 generations from now may not be enough to destroy the genome and that it may take 300,000 generations or 6 million years. (150) You can also look at his work with Mendel's Accountant which in no way suggests 300 generations (if I read the charts correctly). The fact is however, we don't have enough data be sure of how fast the degeneration of the genome is, if it is degenerating at all, so exact time scales are unsure.

Edited by Phydeaux, : No reason given.


This message is a reply to:
 Message 30 by PaulK, posted 11-18-2009 3:26 AM PaulK has responded

Replies to this message:
 Message 36 by PaulK, posted 11-18-2009 11:07 AM Phydeaux has responded

    
Phydeaux
Junior Member (Idle past 3493 days)
Posts: 13
Joined: 11-17-2009


Message 33 of 53 (535835)
11-18-2009 9:39 AM
Reply to: Message 31 by slevesque
11-18-2009 4:24 AM


Re: Epistasis and fitness
You can read prologue along with page 46 for were I'm getting my information.

quote:
So well I would think that he is considered knowledgeable enough to peer-review papers on the subject, than he probably is enough to write on it.

Fair enough.


This message is a reply to:
 Message 31 by slevesque, posted 11-18-2009 4:24 AM slevesque has not yet responded

Replies to this message:
 Message 34 by Wounded King, posted 11-18-2009 10:21 AM Phydeaux has not yet responded

    
Wounded King
Member (Idle past 2385 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


(1)
Message 34 of 53 (535837)
11-18-2009 10:21 AM
Reply to: Message 33 by Phydeaux
11-18-2009 9:39 AM


Re: Epistasis and fitness
quote:
So well I would think that he is considered knowledgeable enough to peer-review papers on the subject, than he probably is enough to write on it.

Fair enough.

This doesn't necessarily follow. People can frequently suggest who they would like to peer review their article, it doesn't follow that the journal editors chose someone because they were particularly suited for the job. Without more details of who submitted the paper, etc ..., we can't really make any conclusions. I have to say that 5 peer reviewers sounds like a lot to me, and common practice is to have peer review performed anonymously.

This sounds to me like it is based on Walter ReMine's paper submitted to 'Theoretical population biology' which was in fact subsequently rejected and published in a creationist journal. It wouldn't surprise me if ReMine recommended Sanford as a reviewer for his paper.

TTFN,

WK


This message is a reply to:
 Message 33 by Phydeaux, posted 11-18-2009 9:39 AM Phydeaux has not yet responded

    
Coyote
Member (Idle past 396 days)
Posts: 6117
Joined: 01-12-2008


(1)
Message 35 of 53 (535839)
11-18-2009 10:58 AM
Reply to: Message 26 by slevesque
11-18-2009 2:08 AM


Re: Deleterious mutations
You always seem to be bringing up the fall for whatever reason I don't know.

When folks become ardent creationists they accept the beliefs of their particular brand of creationism. Many organizations, such as AiG, the Institute for Creation Research, and the Creation Research Society, have a code of beliefs to which all members must subscribe. These are readily available on the web with minimal searching, and will help one understand what the beliefs of the various groups are, and how they require all members to abide by those beliefs.

One of those religious beliefs is in "the Fall." Another is belief in a young earth. Many ardent creationists believe in both, ignoring scientific evidence when it conflicts with scripture.

I think that these beliefs color the thinking of some creationists when they attempt to do science. This pertains directly to the question of "genetic load" because if one is looking at evolution as the product of billions of years, vs. just 6,000 years, one will see the accumulation of deleterious mutations quite differently. And when one believes in "the Fall" it is a natural tendency to blame that for deleterious mutations in the first place!

That is why I have brought up "the Fall" in this thread. I think belief in that, along with belief in a young earth, are influencing the debate concerning genetic loading. I don't know to what degree it may be subconscious, but in either case it is not very good science to rely on mythical events as a fundamental part of one's argument.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 26 by slevesque, posted 11-18-2009 2:08 AM slevesque has not yet responded

  
PaulK
Member
Posts: 15461
Joined: 01-10-2003
Member Rating: 2.9


(1)
Message 36 of 53 (535840)
11-18-2009 11:07 AM
Reply to: Message 32 by Phydeaux
11-18-2009 9:25 AM


Re: Deleterious mutations
So, if I understand correctly, either Crows figures are a severe overestimate or Sanford's model is wrong and selection did remove mutations more efficiently before modern medicine. If not, then what is Sanford's explanation for why we do not see the crash that his model predicts using Crow's figures ?

This message is a reply to:
 Message 32 by Phydeaux, posted 11-18-2009 9:25 AM Phydeaux has responded

Replies to this message:
 Message 37 by Phydeaux, posted 11-18-2009 11:28 AM PaulK has responded

    
Phydeaux
Junior Member (Idle past 3493 days)
Posts: 13
Joined: 11-17-2009


Message 37 of 53 (535845)
11-18-2009 11:28 AM
Reply to: Message 36 by PaulK
11-18-2009 11:07 AM


Re: Deleterious mutations
Sanford was basing the 300 generation thing on Crow's estimates of a decline of 1% per generation. This came from a paper by Crow. I just now looked it up and this is what it states:

quote:
If we are like Drosophila, the decrease in viability from mutation accumulation is some 1 or 2% per generation.(Crow, J.F. 1997. The high spontaneous mutation rate: is it a health risk? PNAS 94:8380-8386)

Sanford's calculations with Mendel's Accountant use perimeters of humans rather than Drosophila. Maybe that is why.

Sanford's model still sees a crash, but it isn't in 300 generation. He never claimed it is 300 generations. As far as I can tell, he was only using Crow's model to prove that even with his numbers we see a crash. He wasn't trying to prove that 300 generations is the correct time.


This message is a reply to:
 Message 36 by PaulK, posted 11-18-2009 11:07 AM PaulK has responded

Replies to this message:
 Message 38 by PaulK, posted 11-18-2009 12:20 PM Phydeaux has responded

    
PaulK
Member
Posts: 15461
Joined: 01-10-2003
Member Rating: 2.9


Message 38 of 53 (535853)
11-18-2009 12:20 PM
Reply to: Message 37 by Phydeaux
11-18-2009 11:28 AM


Re: Deleterious mutations
quote:

Sanford's model still sees a crash, but it isn't in 300 generation. He never claimed it is 300 generations. As far as I can tell, he was only using Crow's model to prove that even with his numbers we see a crash. He wasn't trying to prove that 300 generations is the correct time.

But why is the number wrong ? What factor is different to account for a difference of (maybe) 6 orders of magnitude ? Come to that, what about drosophilia ? Their lifecycle is much quicker than the human one, so that 300 generations would take only a few decades. If selection cannot keep drosophilia adequately fit, why are they still around ?

Moreover, Crow gives reasons to think that the mutation rate in humans is significantly higher in humans, than in drosophilia. How would that help humans to last longer ?

There are a lot of questions here, and the answers I'm seeing don't seem to add up.


This message is a reply to:
 Message 37 by Phydeaux, posted 11-18-2009 11:28 AM Phydeaux has responded

Replies to this message:
 Message 39 by Phydeaux, posted 11-18-2009 12:31 PM PaulK has responded
 Message 41 by Wounded King, posted 11-18-2009 1:56 PM PaulK has not yet responded

    
Phydeaux
Junior Member (Idle past 3493 days)
Posts: 13
Joined: 11-17-2009


Message 39 of 53 (535855)
11-18-2009 12:31 PM
Reply to: Message 38 by PaulK
11-18-2009 12:20 PM


Re: Deleterious mutations
Look, I could go through and try to find out what was wrong with Crow's model, but I really see his model as irrelevant. If Crow's model is wrong, that doesn't mean Sanford's model is as well and it doesn't mean the genome is not deteriorating. I don't really care about Crow's model.

This message is a reply to:
 Message 38 by PaulK, posted 11-18-2009 12:20 PM PaulK has responded

Replies to this message:
 Message 40 by PaulK, posted 11-18-2009 1:04 PM Phydeaux has not yet responded

    
PaulK
Member
Posts: 15461
Joined: 01-10-2003
Member Rating: 2.9


Message 40 of 53 (535864)
11-18-2009 1:04 PM
Reply to: Message 39 by Phydeaux
11-18-2009 12:31 PM


Re: Deleterious mutations
So far as I can tell the model is Sanford's. Certainly there's no mention of such a model in Crow's paper. Crow argues that selection can adequately eliminate sufficient harmful mutations.

So I am going to ask again. According to the quote you produced Sanford claims that using Crow's estimate - which was conservative - the population should crash in 300 generations, even with the selective effects that Crow believes to be adequate to prevent a crash altogether.

In reality it does not happen, even to drosophilia. So either Crow's estimate is badly wrong, or Sanford's calculations are equally badly wrong. Which is it ?


This message is a reply to:
 Message 39 by Phydeaux, posted 11-18-2009 12:31 PM Phydeaux has not yet responded

Replies to this message:
 Message 42 by slevesque, posted 11-18-2009 3:34 PM PaulK has responded

    
Wounded King
Member (Idle past 2385 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 41 of 53 (535869)
11-18-2009 1:56 PM
Reply to: Message 38 by PaulK
11-18-2009 12:20 PM


Re: Deleterious mutations
Moreover, Crow gives reasons to think that the mutation rate in humans is significantly higher in humans, than in drosophilia.

This is almost certainly the case. Most current estimates put the human value of U (the genomic deleterious mutation rate) at ~4 compared to a value of ~1 in Drosophila (Eory et al., 2009). Interestingly the last author on the paper is Keightley who Crow mentioned in his 1997 paper as thinking the Drosophila rate estimates were too high.

TTFN,

WK


This message is a reply to:
 Message 38 by PaulK, posted 11-18-2009 12:20 PM PaulK has not yet responded

    
slevesque
Member (Idle past 2931 days)
Posts: 1456
Joined: 05-14-2009


Message 42 of 53 (535890)
11-18-2009 3:34 PM
Reply to: Message 40 by PaulK
11-18-2009 1:04 PM


Re: Deleterious mutations
It is because, as WK said, you are assuming the number of mutations per individual per generation is the same in Drosophilia then in humans. But of course it is not.

The reason for this is simple: the mutations happen during transcription. Since both Drosophilia and humans are both eukaryotic, they have the same transcription method, and so the same amount of mutations per transcription. However, since a human generation is 20years, by the time the individual does reproduce, his reproductive cells that produce the spermatozoides (sorry I don't have the exact terminology) have duplicated a lot more than if it was only a half-year generation for example, and so they have more mutations per generation

And so, the smaller generation time is actually and advantage to last longer, since if natural selection can only act after 20years of ccumulatio nin the case of humans, in the case of drosophilia, it can act every couple of days, which in turn runs counter to mutation accumulations. In fact, the most optimal is selection between each transcription, which happens in the unicellulr organisms.

AbE This reply would be actually more approriate in a reply to message no38 by PaulK, I clicked the wrong one.

Edited by slevesque, : No reason given.


This message is a reply to:
 Message 40 by PaulK, posted 11-18-2009 1:04 PM PaulK has responded

Replies to this message:
 Message 43 by PaulK, posted 11-18-2009 5:16 PM slevesque has responded
 Message 44 by Wounded King, posted 11-18-2009 5:30 PM slevesque has responded

  
PaulK
Member
Posts: 15461
Joined: 01-10-2003
Member Rating: 2.9


Message 43 of 53 (535922)
11-18-2009 5:16 PM
Reply to: Message 42 by slevesque
11-18-2009 3:34 PM


Re: Deleterious mutations
quote:

It is because, as WK said, you are assuming the number of mutations per individual per generation is the same in Drosophilia then in humans. But of course it is not.

That's wrong. As WK said the rate is higher in humans, making the problem even worse.
(And it wasn't my assumption either - Crow used it as a conservative estimate, and Sanford ran with it).

quote:

And so, the smaller generation time is actually and advantage to last longer, since if natural selection can only act after 20years of ccumulatio nin the case of humans, in the case of drosophilia, it can act every couple of days, which in turn runs counter to mutation accumulations. In fact, the most optimal is selection between each transcription, which happens in the unicellulr organisms.

It is only an advantage in so far as it reduces the number of mutations per generation. Which confirms my point that humans are in an even worse situation, on a per-generation basis.


This message is a reply to:
 Message 42 by slevesque, posted 11-18-2009 3:34 PM slevesque has responded

Replies to this message:
 Message 46 by slevesque, posted 11-18-2009 5:45 PM PaulK has responded

    
Wounded King
Member (Idle past 2385 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 44 of 53 (535925)
11-18-2009 5:30 PM
Reply to: Message 42 by slevesque
11-18-2009 3:34 PM


Re: Deleterious mutations
You are getting transcription, RNA synthesis from a DNA template, mixed up with DNA replication, DNA synthesis from a DNA template. One reason for the difference between human and Drosophila is simply the size of the genome. Since the rates are calculated per genome an organism with a genome 4 times the size would be expected to have a 4 times higher rate everything else being equal, given an equal rate of mutation over a specific length of DNA. In fact the human genome is more than 10 times the size, but a lot of that is structural non-coding DNA which probably accounts for some of the difference in rate.

There is an increase in mutations in germ cells with age, but it is not significant enough to have had a major effect until very recently as parental ages have been increasing. Even earlier this century the ages of most parents would not have made this a significant factor. This is most noticable in the male germ cells which are constantly regenerated.

I don't think your ideas here really have anything to do with the differences in deleterious mutation rates per genome. You seem to have things a bit mixed up, your explanation is more for why humans are susceptible to cancers and Drosophila are not.

TTFN,

WK

Edited by Wounded King, : No reason given.


This message is a reply to:
 Message 42 by slevesque, posted 11-18-2009 3:34 PM slevesque has responded

Replies to this message:
 Message 45 by slevesque, posted 11-18-2009 5:44 PM Wounded King has responded

    
slevesque
Member (Idle past 2931 days)
Posts: 1456
Joined: 05-14-2009


Message 45 of 53 (535927)
11-18-2009 5:44 PM
Reply to: Message 44 by Wounded King
11-18-2009 5:30 PM


Re: Deleterious mutations
Yeah my bad, I usd the word transcription instead of replication.

But, if we would reproduce at age 10, wouldn't the germ cells have replicated twice as less, and so the DNA they would contain would have had twice as less mistakes as compared to the parents DNA ? If not, why ?


This message is a reply to:
 Message 44 by Wounded King, posted 11-18-2009 5:30 PM Wounded King has responded

Replies to this message:
 Message 47 by Wounded King, posted 11-18-2009 6:03 PM slevesque has responded

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019