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Science! Ask you question here. Biscuits NOT included and answers not guaranteed.
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I've a question for the science nerds!
Is the mutution process something that is constantly happening or something that's is activated by external pressures?
Hallelujah, at last we have some sensible questions to discuss.
I would agree with Robin in that mutation is constantly happening but is also something which is affected by enviromental factors.
Our current estimate of mutation rate suggests that each child is born with about 128 mutations compared to the genomes of their parents.
Mutation rates in humans. II. Sporadic mutation-specific rates and rate of detrimental human mutations inferred from hemophilia B.
We also know that only, at most, about 4 of these 128 mutations are actually deleterious or harmful mutations.
The X Chromosome and the Rate of Deleterious Mutations in Humansanother question.
with regard to a new species arising, is there a standard number of generations for a new one to appear or does it depend on the pressures causing the mutation?With regards to the early stages of speciation, does it follow some sort of template? I.e. a single offspring of the new species is born, or would they be born in clusters within the population.
Apologies if the questions seem scattershot, but it's just how they're popping up in the head.
The short answer to your question is that no, there is no standard number of generations for a new species to appear.
To answer it in more depth, I suggest that you look at speciation not from a mutation based viewpoint but a population based one.
Speciation occurs when two groups who share common ancestry can no longer reproduce with viable offspring. One of the primary causes of speciation is geographic isolation. When you have two groups both originating from a parent population which are separated by geography (mountains, oceans etc.) the two groups will continue to diverge because of the lack of gene flow between them. This means that a mutation which confers a benefit in a creature in group A will be propagated through the entire group. Group B meanwhile will lack this mutation due to the lack of any sexual interaction between the groups. As more instances of this occur, the more the two populations become genetically distinct from each other. Eventually, even if the two groups are reunited the probability that they will be genetically similar enough to produce offspring is remote.
Speciation is a complex phenomenon, so much so that we have had to categorise different modes of speciation: allopatric, peripatric, parapatric and sympatric. There's a very nice introductory article on speciation here:
Modes of speciation
So, coming back to your second question, looking at the question of speciation from the point of view of groups within a population will probably help you understand the issue better than mutations to an individual organism.0 -
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OMG! Spoiler!It's a bit more complicated than that.
Microorganisms have certainly changed immensely. The two main families of prokaryotes are bacteria and archaea. Prokaryotes don't separate their DNA from the rest of the cell by putting it in a nucleus. In fact, they have no membrane-bound organelles. Archaea and bacteria used to be thought of as just bacteria, but archaea have significantly different biochemistry (they use ether lipids in their cell walls, for example, and several of their metabolic systems have more in common with eukaryotes (DNA in a nucleus, like us) than bacteria). There are other differences, but I'm not getting paid here and Wikipedia is right there...
The diversity in prokaryotes is orders of magnitude higher than you'll see in prokaryotes. Some bacteria have circular chromosomes, some have linear ones. Some have hundreds of plasmids (sort of extra chromosomes, small circles of DNA with interesting genes like antibiotic resistance), some don't really bother with them. Some are very 'social' forming biofilms where multiple species of bacteria can grow, signalling and reacting to each other to maintain a stable community, such as the really very useful families of bacteria in your intestines. Neurogastroenterology (yes, it's a real thing) is discovering how communities of bacteria don't just communicate with bacteria. They communicate and work with their host for the benefit of both. Gut bacteria can affect our brains, and our moods can affect our gut bacteria. It's a complicated system and we're just getting to grips with it, but there's some amazing stuff coming out of it already, like better ways to treat cystic fibrosis patients, probiotic supplements for the elderly to get their gut bacteria back to the kind of diversity seen in healthier younger people, stuff like that.
The whole idea of bacteria being malicious bugs is something that needs to stop, really. They don't actively seek out poor innocent people to infect, and an infection is more a case of the microbe being in the wrong place at the wrong time. It's usually a death sentence for the microbe in question, they'd be much happier wandering about in the soil or living in that camel's rectum without humans bungling along and uprooting them.
Given enough time, a host/parasite relationship often becomes commensal (nobody is inconvenienced by one depending on the other) and may even become symbiotic (living together actually benefits both organisms). That's pretty close to what happened with eukaryotic cells. See, eukaryotic cells contain loads of little membrane-bound organelles which do a lot of the work of copying out DNA, destroying intruders and the like. Mitochondria are a classic example. It turns out they have their own DNA, separate from the chromosome. This, along with other factors I won't get into because this post is already big enough, is good evidence that mitochondria and other mini-organs used to be bacteria that evolved a symbiotic relationship with other cells. A single eukaryotic cell is, in a sense, actually a community of prokaryotes, albeit one where the individuality of the prokaryotes has long since been subsumed into the single identity of the cell they all live in. Hell of an evolutionary jump there. Clever way to ensure you survive.
Humans bringing bacteria to new places is a bit redundant, it seems no matter where we go, bacteria have already been there for millions of years. The top of Everest, the bottom of the ocean floor, inside massively acidic 300 degree high pressure water springs... There's nowhere it seems they CAN'T evolve to live and survive.
J C completely misses the point of evolution by saying "millions of years later they're still bacteria". You're damn right they're still bacteria, they've evolved to become really good at being bacteria. And millions of years after the last human dies off and the planet becomes a radioactive wasteland, they'll still be there, winning at evolution.0 -
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HURRY UP WITH THE BISCUITS!Mitochondria are a classic example. It turns out they have their own DNA, separate from the chromosome.
Does that Mitochondria mean the same thing as Mitochondrial Eve? (Is that a stupid question?)
I find this whole area fascinating.
However, to your normal lay person it's vast and so complex that it is difficult to know where to even begin if you want to know more.
23andme have updated their site recently. (For those who don't know, they do up your DNA)
I now have easy access to all my data:
Most of the DNA inside each of your body's cells is divided into pieces called chromosomes, with the remaining DNA found in tiny loops inside your cells' mitochondria. Click below on any chromosome or the mitochondrial loop to see the genes and SNPs it contains.
Problem there is, I'll be needing a fecking degree to understand it!
Is there a particular site with an idiots guide?
I can click on each one of my chromosomes and there is a vast amount of data.
How do I go about reading it? Is there any point to trying to read it?
This for instance:
intergenic 18674 rs10195681 A or C CC
Does the above make sense to you Sarky?0 -
FYI: This is Option Number Twenty-Five. Isn't this being a bit, uh, mean on the hamsters?Does that Mitochondria mean the same thing as Mitochondrial Eve? (Is that a stupid question?)
I find this whole area fascinating.
However, to your normal lay person it's vast and so complex that it is difficult to know where to even begin if you want to know more.
23andme have updated their site recently. (For those who don't know, they do up your DNA)
I now have easy access to all my data:
Most of the DNA inside each of your body's cells is divided into pieces called chromosomes, with the remaining DNA found in tiny loops inside your cells' mitochondria. Click below on any chromosome or the mitochondrial loop to see the genes and SNPs it contains.
Problem there is, I'll be needing a fecking degree to understand it!
Is there a particular site with an idiots guide?
I can click on each one of my chromosomes and there is a vast amount of data.
How do I go about reading it? Is there any point to trying to read it?
This for instance:
intergenic 18674 rs10195681 A or C CC
Does the above make sense to you Sarky?
Not sure if this will help: https://customercare.23andme.com/forums/20790464-Understanding-Your-Results0 -
That paper doesn't seem to control for age of the father, so is is right to assume that the 128 mutations figure is the average for all males?
I wouldn't think so no. The partner study to the one in my last post details the sampling methodology in more detail.
Mutation Rates in Humans. I. Overall and Sex-Specific Rates Obtained from a Population Study of Hemophilia B
I would guess that the average, such as it is, would hold for people at typical age of first child but I expect that the spread of the data is too large for it to hold as an average for all parents.I'm asking since women produce their eggs at birth (so replication errors will be low) while male's sperm-producing cells reproduce constantly, so they'll carry a greater and greater number of reproduction errors as the male ages.
In general, yes. The studies above found that the average ratio of male-female mutation rate is 8.64. Having said that, however, the female mutation rate is affected similarly by age so I would expect this ratio to decrease with increasing age. If you look at Down's syndrome, for example:
we can see that the incidence changes from approximately 1 in 2300 for a 20-year old woman to 1 in 100 for a 40-year old. Other chromosomal errors also increase with maternal age.0 -
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FYI: This is Option Number Twenty-Five. Isn't this being a bit, uh, mean on the hamsters?This thread is now fab (ha!).....koth, thanks for the great questions!
It just seemed like a wasted opportunity if I didn't throw questions to the folk that seem to have a good understanding of biology and evolution.
At least they're receptive to answer questions and providing evidence/links to support what they post.If you can read this, you're too close!
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