Odds of Mutation

[gmacrider]

What are the odds of the same heritable mutation occuring in more than one individual during a period of time that spans roughly a couple of generations?

 

I guess that's tough to answer. I just find it odd that several individuals in a population would have the same mutation at the same time, resulting in numerous offspring that have an advantage over the rest of the population.

[JustStuit]

I'm pretty sure one individual with a mutation has a chance of passing it down and then, if beneficial or passive, it will be spread around.

[RyanJ]

I'm pretty sure one individual with a mutation has a chance of passing it down and then, if beneficial or passive, it will be spread around.

 

Yup, true. There is however one thing, if its on the "Y" chromosome its less likley to be passed then the "X" chromosome simple because you have:

 

Female: XX

Male: XY

 

So there is a greater chance of the mutation on the X being passed on rather then one on the Y being passed on

 

There are a few odd mutations on the "Y" chromosome for example that females don't normally get like colour blindness...

 

Cheers,

 

Ryan Jones

[ecoli]

What are the odds of the same heritable mutation occuring in more than one individual during a period of time that spans roughly a couple of generations?

 

considering how many genes we have, it would be pretty low. But, there are too many factors involved to give an exact statistic. Consider self-repairing mechanisms, the fact that mutation events are random, the fact that mutation rate is dependant on the individual's biology and lifestyle... you get the idea.

[Moonquake]

There are a few odd mutations on the "Y" chromosome for example that females don't normally get like colour blindness...

Colour blindness is a mutation on the 'X' chromosome.

 

As for the rest of your post, they're both just as likely to be passed on.

[RyanJ]

Colour blindness is a mutation on the 'X' chromosome.

 

As for the rest of your post' date=' they're both just as likely to be passed on.[/quote']

 

Not really, a mutation on the Y chromosome cannot be passed to a female so its less likley to be passed on... r maybe not, its late and statistics confuse me at the best of times

 

Cheers,

 

Ryan Jones

[Moonquake]

Not really' date=' a mutation on the Y chromosome cannot be passed to a female so its less likley to be passed on... r maybe not, its late and statistics confuse me at the best of times

 

Cheers,

 

Ryan Jones[/quote']

If a mutation happens in a single X chromosome or a single Y chromosome in a generation, it's just as likely to be passed on either way. If it happens to an X chromosome in a male or a female it would be passed on to half his/her offspring. If it happened in the Y of a male instead it would be passed on to half his offspring.

[Moonquake]

I just find it odd that several individuals in a population would have the same mutation at the same time, resulting in numerous offspring that have an advantage over the rest of the population.

When do you think this has happened? Like Juststuit said you only need it to happen once to start it spreading through their offspring. Several individuals don't need to mutate.

[Earth_Muffin]

What are the odds of the same heritable mutation occuring in more than one individual during a period of time that spans roughly a couple of generations?

 

.

 

Depends on whether the initial carrier is homozygous or heterozygous as to how many offspring would be affected and to how profound the affects would be. For instance, in a society in which there is an "alpha male" perse, who produces a total of 8 offspring, as a homozygous carrier the mutation could occur in as many as 4 of the offspring, whereas if he was a heterozygous carrier, the mutation could occur in as many as 2. If the initial carrier is female, the likelihood of affecting a large portion of the population is somewhat reduced, as females are limited as to how many offspring they can produce in a lifetime. If a female homozygous carrier produced 4 offspring, 2 could potentially become carriers, whereas if she was a heterozygous carrier, the chances of passing the mutation to offspring is reduced to perhaps 25% at best, which, if she produced 4 offspring, 1 would be affected.

 

Moving on to the second generation, you can see from the above model how these numbers would multiply, providing the mutation was favorable to natural selection. It should be noted that negative mutations often do not simply "die out". I doubt there is a single person in the world population that is not a carrier for some harmful genetic mutation, whether it be Tay Sachs, sickle cell, or whatever the case may be. What's important to note here is that being a carrier doesnt necessarily mean the "mutant" gene will present itself. It should also be noted that some mutations that are considered harmful also have benefits to those within the region where the mutation first presented itself. For instance, persons in which sickle cell is present also carry some resistance to malaria.

[gmacrider]

Thanks all for the info. I was just trying to understand how mutation drives evolution. So it sounds like any new heritable characteristic in a population can be trace back to a mutation in the gametes of a SINGLE individual. I hadn't thought it through before and was under the impression new (similar) mutations would occur in several members of the population at the same time, but now that sounds highly unlikely.

[RyanJ]

Thanks all for the info. I was just trying to understand how mutation drives evolution. So it sounds like any new heritable characteristic in a population can be trace back to a mutation in the gametes of a SINGLE individual. I hadn't thought it through before and was under the impression new (similar) mutations would occur in several members of the population at the same time, but now that sounds highly unlikely.

 

Its possible but unlikley, some traits remain dormant and can build up over time especially in closed populations

 

Cheers,

 

Ryan Jones

[Prime-Evil]

Does that mean that many or perhaps even most successful mutations start off dormant?

[CharonY]

In the simplest case there are two pools on which selection can work on. First are mutations that only exist but have not yet been subjected to selective sweeps (that is, they are already spread in the population but are dormant as stated above) or they are new traits or alleles that are not fixed yet.

 

In the latter case (and that is probably what gmacrider is thinking of) the frequency of the new trait being fixed in the population (that is not being directly eliminated after selective sweeps) is a function of the frequency of its occurence and its effect on the fitness of its carrier. If the increase of fitness is vast, only few occurences (or as proposed above, possibly one single mutation) might be needed in the population before it gets fixed and may start to spread. But this is a rather rare case. In most cases the effects beneficial effects are very low. As such most models would require at least a moderate frequency of occurence of a particular mutation to allow it become a fixed element of the gene pool.

[SkepticLance]

Odds of mutation is not a question for which there is a single, simple answer. Too many variables. Mutations in general are very common. It happens all the time inside our bodies. DNA is damaged. DNA is repaired. DNA is damaged and not repaired, and the cell dies. DNA is damaged and not repaired and the cell turns cancerous. The cancerous cell gets wiped out by our immune system, or turns into a tumour. Etc.

 

The frequency of mutation also depends on the type of mutation. Some are relatively common; some rare. To be passed on to the next generation, the mutation must have happened in a germ cell, about to become a gamete, and this is not too common. However, over a few billion years of evolution, a hell of a lot of mutations build up in the population.

 

So to your question. It depends.

[Cap'n Refsmmat]

Thanks all for the info. I was just trying to understand how mutation drives evolution. So it sounds like any new heritable characteristic in a population can be trace back to a mutation in the gametes of a SINGLE individual. I hadn't thought it through before and was under the impression new (similar) mutations would occur in several members of the population at the same time, but now that sounds highly unlikely.

Just remember that several mutations can happen in different individuals in the same generation and end up spread among offspring as well. Evolution doesn't work one mutation at a time.

[Dr. Dalek]

Sometimes it does occur one mutation at a time, especially in complex organisms where several genes are used to control a single trait. Multiple mutations occurring in the same set of genes are necessary to change a significant trait and can take thousands of years for that single trait to be altered.