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Author Topic:   Is there any proof of beneficial mutations?
Percy
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Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 98 of 166 (580584)
09-10-2010 7:30 AM
Reply to: Message 93 by dennis780
09-10-2010 12:03 AM


Re: Cause of mutation?
dennis780 writes:
quote:
if your are suggesting that "instinctive behaviour" can change genetic code deliberately to produce a specific outcome, then you are still wrong.
So bacteria do not respond to their environments? Because even Crashfrog proved you wrong.
You misunderstood both Greyseal and Crashfrog. While living bacteria do, of course, respond to their environment, specific mutations are not part of that response. Mutations occur randomly, usually during reproduction, binary fission in the case of bacteria. Random mutations can also occur during the lifetime of a bacterium, though this is less frequent.
Environmental conditions can cause an increase in the mutation rate of some types of genes of bacteria, but cannot direct specific mutations, and certainly have no specific outcome in mind.
--Percy

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 Message 93 by dennis780, posted 09-10-2010 12:03 AM dennis780 has not replied

Replies to this message:
 Message 100 by Dogmafood, posted 09-10-2010 7:41 AM Percy has replied

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


(1)
Message 104 of 166 (580598)
09-10-2010 8:08 AM
Reply to: Message 100 by Dogmafood
09-10-2010 7:41 AM


Re: Cause of mutation?
Dogmafood writes:
I find it truly astounding how successful organisms are at randomly producing a particular mutation that lends them immunity to a particular randomly appearing pathogen. The odds seem to be so incredibly high.
Here's a description of a simple experiment that illustrates what happens. A scientist places a billion bacteria in a petri dish with a growth medium containing a nutrient the bacteria cannot metabolize. Bacteria that could metabolize this nutrient would have a great competitive advantage over bacteria that did not. The bacterial genome has a billion nucleotide pairs.
As it happens, a single mutation in one gene would allow the bacteria to metabolize the nutrient, but the odds of this mutation occurring are a billion to one.
But there are a billion bacteria. If each bacterium divides once, what are the odds that one of them will experience the precise necessary mutation. By making some simplifying assumptions it becomes a simple calculation that only takes a half minute on a calculator, so I went ahead and did this, and the odds are 63% that at least one of the billion bacteria will experience that exact mutation. In reality the odds will be affected by factors I ignored, like how many of the other three nucleotides cause the desired effect, but the odds would still be pretty good. We'll be pessimistic and say the real odds are 10% that the needed mutation would occur in a single generation.
So what are the odds that the mutation would arise within 10 generations, which with a 20 minute generation time would only take around 3 hours? We'll assume that the bacterial population size remains at a billion. The odds are 65%.
And what are the odds that the mutation would arise within 100 generations, which would only take a little over a day? The odds are 99.99%.
How about that? If you're willing to wait a single day, it's a virtual certainty that that 1-in-a-billion mutation will occur.
--Percy

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 Message 100 by Dogmafood, posted 09-10-2010 7:41 AM Dogmafood has seen this message but not replied

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 156 of 166 (581050)
09-13-2010 8:19 AM


Beneficial Mutation in Deer Mice
Another example of a beneficial mutation occurs in deer mice, here's a layperson note about it from Discover Magazine: Fast-Track Evolution Gave Rise to Deer Mouse’s Pale Coat
The Sand Hills of Nebraska formed over a period from 15,000 to 8,000 years ago, and deer mice in this region have lighter fur than deer mice elsewhere. Genetic analysis reveals that a mutation for lighter fur occurred in the Agouti gene about 4,000 years ago, evidently as a protective measure. Light-colored deer mice have an estimated 0.5% better chance of survival in the light-colored sands, and over a few thousand years this has caused light coloration to become dominant in the Sand Hills.
Here's a link to the scientific paper in Science, but as always, you need a subscription if you want more than the abstract: On the Origin and Spread of an Adaptive Allele in Deer Mice
--Percy

  
Percy
Member
Posts: 22388
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 165 of 166 (582518)
09-21-2010 6:52 PM
Reply to: Message 164 by dennis780
09-21-2010 5:54 PM


Re: Creation "science" on display
The thread's about evidence for beneficial mutations.
--Percy

This message is a reply to:
 Message 164 by dennis780, posted 09-21-2010 5:54 PM dennis780 has not replied

  
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