# Genetic mutation



## HareBrain (Aug 12, 2009)

I was just wondering (and a brief skim-read of the internet has not provided the answer) has anyone ever isolated a genetic mutation, ie where it can be shown that neither parent has it, but the offspring does?

If no, what advances in technology would be required to do so?

If yes, how common are they, and is it possible to estimate what proportion _might _be beneficial in evolutionary terms?


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## Granfalloon (Aug 12, 2009)

As I understand it Hare, It is very common for genetic "traits" to skip generations (such as red hair - not red hare. _Sorry, I'm terrible._) But you've used the word mutations which are very rare, so I would think whether or not they are beneficial depends entirely on the type of mutation. Webbing between the toes of one's foot might be beneficial for swimming for example. Can they isolate and control those kinds of things? Is that the question?


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## Ursa major (Aug 12, 2009)

Granfalloon said:


> As I understand it Hare, It is very common for genetic "traits" to skip generations (such as red hair - not red hare.


 
Yes: the gene for red hair is recessive and so only exhibits itself when two are present. So, for example, the two types of offspring of a redhead (*RR*) and someone lacking the gene (*NN*) would be *NR* and *RN*; so no redheads in this generation.



(Whether the read hare is dominant depends, at least to some extent at least, on HB's skill as a writer.)


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## chrispenycate (Aug 12, 2009)

I would certainly hope your example was being tested on "lower" species (those with simpler genotypes) rather than humans. And it just so happens that, having a friend who is a specialist in the Triatominae, I can give you an example of the inverse situation.

These are blood-sucking bugs, originating in the Americas (principally in Southern and central regions) As silvatic species (tree living outdoor bugs) move into the sheltered domestic environment, the list of population controls changes, and diminishes. No more predators, no more famines due to loss of prey species. Basically, it reduces to insecticides and internal competition.

The internal competition is the first problem addressed, and insects with less DNA can reach breeding age faster, with less nutrition. Of course, reduced DNA means less diversity, less adaptability; but you've fewer enemies, and, if you've got a bit assymetrical, and can't run away as fast as your ancestors could, who cares? There's no-one running after you, and you can manage more offspring.

So, it becomes a race to dump DNA. You might not have genes that neither of your parents had, but you most certainly lack some that both of them had (much easier in that direction). Of course, this lack of variability means they are very poor at 'learning' insecticides. So spraying houses improves the species. 

Surely the loss of genes constitutes an evolution, too. And it proves that simplification can be a success story.


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## The Judge (Aug 12, 2009)

I don't know.  This is the third time I've tried to post in this thread.  Either senility is catching up with me at an alarming rate - or there are sinister forces at work trying to prevent my earth shattering secrets being revealed...

OK.  Try again.  Again.

Does having 6 fingers on one hand count as a genetic mutation?  It isn't hereditary as far as I'm aware, but it isn't all that uncommon.  

Surely anything which can affect a man's sperm (or a woman's egg?) - eg radiation, toxins - can produce a mutation?  (To avoid this post being pulverised again, I won't make reference to the possibility of an increase in birth abnormalities among the children born to servicemen who had received a cocktail of prophylactic drugs in the Gulf War.)

Is the real question not whether a mutation can arise, but whether that mutation is itself hereditable?  Not that I can help you with that one either. 

J


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## HareBrain (Aug 12, 2009)

Interesting answers all, but what I'm interested in is whether anyone has identified a mutation at the point at which it occurred. (I'm assuming this question makes sense, scientifically. If not, don't be afraid to tell me I'm an idiot!)


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## dustinzgirl (Aug 12, 2009)

HareBrain said:


> I was just wondering (and a brief skim-read of the internet has not provided the answer) has anyone ever isolated a genetic mutation, ie where it can be shown that neither parent has it, but the offspring does?



I have. Three times. Their names are Christopher, Amanda, and Hunter. Or, in their language, Bubbies, Sissies, and Boodas. 



I contributed nothing to this conversation, but I thought I was funny.


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## HareBrain (Aug 12, 2009)

I've just realised that I know even less about genetics than I thought, so perhaps someone could tell me where my understanding falls on the Continuum of Relative Ignorance.

For a mutation to be passed on, it occurs in the reproductive DNA of the parent, right? But that means the reproductive DNA becomes different to the DNA in the rest of the parent's cells, whereas "ideally" they would all be the same - is this so?

Is it possible for a mutation to occur in, say, a skin cell, and have no effect? Or do they occur only in reproductive cells? If so, why? Or, back to my original question, is not enough known about it yet because of the difficulty of observing/measuring this process?


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## chrispenycate (Aug 13, 2009)

Mutations occur in all cells; some cause cancers, most die. Either at the normal time, or much earlier. the loss of a few of your billions of cells doesn't worry you at all. Sometimes, with a plant you will get a mutation in the growing point of a twig, and in time the entire end of a branch is slightly different from the rest of it.'Slightly being the operative word. But only when you go through a single cell point can this modify an entire organism, and, in time, a whole line of organisms, and, in animals, this means at the level of a gamete.

It would be extremely time-consuming at the present level of the art to do a sufficient number of gene scans to a sufficient accuracy to detect what must be a fairly rare occurrence. But we'd be very sure of the paternity of a large number of children.


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## The Judge (Aug 28, 2009)

HareBrain - not sure if you've seen the new post re the deer mice in the science/nature section.  Scientists have worked out a new pale-coat gene came into existence barely 4,000 years ago in these mice, which has proved immensely beneficial to them (to the mice, that is, not to the scientists) since they are living in a particular sandy area.  The article is brief but interesting - and it refers to a fuller report that might answer some of your questions.

J


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## Ursa major (Aug 28, 2009)

HareBrain said:


> Interesting answers all, but what I'm interested in is whether anyone has identified a mutation at the point at which it occurred. (I'm assuming this question makes sense, scientifically. If not, don't be afraid to tell me I'm an idiot!)


 
I don't know how close to the point of mutation you want to be, but mutations that may directly affect humans are occuring quite frequently and regularly (if that's the right word) in various viruses that impact human health: hence the variety of 'flu viruses and (I think) the difficulties in combatting HIV.



You might try getting hold of a copy of *Almost Like a Whale*, Steve Jones's "updating" of *On the Origin of Species*.


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## The Judge (Aug 28, 2009)

Ursa major said:


> You might try getting hold of a copy of *Almost Like a Whale*, Steve Jones's "updating" of *On the Origin of Species*.



Or you might not, Harebrain - that is if you like books to be well-written and non-repetitive.  I regularly read a column Steve Jones writes and I've enjoyed his articles - and there were some good stories and interesting facts in the book - but overall it was a massive disappointment.  I don't think I ever did manage to finish it.  Having said that, I think part of the problem may have been he deliberately replicated Darwin's structure in writing it: I've no idea if 'Origin' suffers the same flaws.

J


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## Granfalloon (Aug 29, 2009)

HareBrain said:


> "... perhaps someone could tell me where my understanding falls on the Continuum of Relative Ignorance."


AKA - CORI? Very funny Hare. I love it. I'm afraid it would be just as impossible to place you on that scale as it would to answer your question. The biggest difficulty is, it's all about statistics. AKA "chances". Try this link for a kind of "bigger picture " look at the situation:
HowStuffWorks "Evolution"




HareBrain said:


> For a mutation to be passed on, it occurs in the reproductive DNA of the parent, right? But that means the reproductive DNA becomes different to the DNA in the rest of the parent's cells, whereas "ideally" they would all be the same - is this so?


 In order to be passed on, they must be in the DNA sequence. From a cursory amount of research, the answer to this question is that the Mother and Father each contribute a "set" of chromosomes (known as XX: female, XY:male) and only the male gametes can be either. That's explained here:
Gamete - Wikipedia, the free encyclopedia
Also, within each "zygote" (the combination cell of the mother and father) there are now 4 sets of chromosomes which "line up" and connect (23 from mom and 23 from dad) which gives us 46 chromosomes, each of which have  thousands of genes. They go through a process called: Homologous recombination - Wikipedia, the free encyclopedia
Humans are in one of three classes of cells known as: 
Eukaryote - Wikipedia, the free encyclopedia

By the way it may be a bit of a misnomer to use the phrase "reproductive DNA". (Try looking it up.)



HareBrain said:


> Is it possible for a mutation to occur in, say, a skin cell, and have no effect? Or do they occur only in reproductive cells? If so, why? Or, back to my original question, is not enough known about it yet because of the difficulty of observing/measuring this process?


In order to be passed on, they must be in the DNA sequence. Also, apparently neutral mutation is very common:
Human genetic variation - Wikipedia, the free encyclopedia

At least we can all say that we are here because were the best swimmers (on our father's side ) in the group. Good question though.


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## Nik (Aug 29, 2009)

This may be relevant...
We are all mutants: Measurement of mutation rate in humans by direct sequencing
quote:
We are all mutants: Measurement of mutation rate in humans by direct sequencing

August 27th, 2009 An international team of 16 scientists today reports the first direct measurement of the general rate of genetic mutation at individual DNA letters in humans. The team sequenced the same piece of DNA - 10,000,000 or so letters or 'nucleotides' from the Y chromosome - from two men separated by 13 generations, and counted the number of differences. Among all these nucleotides, they found only four mutations. 
...
...
"These four mutations gave us the exact mutation rate - one in 30 million nucleotides each generation - that we had expected," says the study's coordinator, Chris Tyler-Smith, also from The Wellcome Trust Sanger Institute. "This was reassuring because the methods we used - harnessing next-generation sequencing technology - had not previously been tested for this kind of research. New mutations are responsible for an array of genetic diseases. The ability to reliably measure rates of DNA mutation means we can begin to ask how mutation rates vary between different regions of the genome and perhaps also between different individuals." 
/quote


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## HareBrain (Aug 29, 2009)

Thanks for the links. When I have more time and more brains next week I'll try to have a look.


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## Ursa major (Aug 29, 2009)

HareBrain said:


> When I have ... more brains next week.


 


* Locks doors and puts crash helmet on. *


This wasn't the kind of mutation we were talking about.


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