The Genetics of Mars One

[ydoaPs]

Mars One is a proposed colony on Mars. The colonists are chosen via reality TV. The colony starts with 4 people and every 2 years, 4 more people join. Having babies is discouraged until after the first 5 years due to safety concerns.

 

Now, that means that the population size when breeding is first "allowed" is only 8. Doesn't that mean founder effect is HUGE? Now, there's horizontal gene flow every 2 years (4 more people arrive). Is this rate of horizontal gene flow enough to offset the genetic drift and founder effect?

[jp255]

It is quite likely that there would be a loss of genetic variation. The likelihood increases the smaller the emigrating population becomes. The liklihood that some alleles will be lost and others become fixated also increases the smaller the emigrating population becomes. Since the population is small, it is likely there will be loss of variation.

 

The rate of gene flow in this example (assuming the Mars inhabitants don't become prejudiced and decide to inbreed) is very small and will quickly become insignificant (occurs sometime after births exceed immigration). Assuming 20 years per human generation, only 40 people will come to Mars per generation. Depending on what assumptions are made, births exceeding immigration could occur over a small number of generations (the immigration would help to initially increase the population, but will gradually become less significant as the births will rise as a consequence). Since the gene flow is one direction only, the populations are destined to diverge over time (especially since the immigration rate will eventually be insignificant, once the population rises).

 

Yes the founder effect question. It is a likely possibility.

 

As for the other question, can gene flow offset the effects of genetic drift and the founder effect. I would say no when considering the scenario in the long term because the gene flow becomes insignificant. Gene flow essentially acts as a buffer between two populations, the more of it that occurs the more similar (in terms of genetic variation) the two populations will be. If anything, there could be partial compensation in the early generations (e.g an allele is lost by genetic drift in the next generation on Mars, but immigration re-introduces that allele), but the allele frequencies will not be restored to be the same as the original population on Earth (that will be down to genetic drift, more so as the gene flow effect weakens as immigration becomes insignificant).

 

I have a feeling the term you used "Horizontal gene flow" will lead to confusion. "Horizontal gene transfer" refers to gene flow between individuals (e.g bacteria) from the same generation (i.e not offspring). So it's probably best to say veritcal gene flow, or just gene flow.

[michel123456]

It is a bottleneck.

Mars One is a proposed colony on Mars. The colonists are chosen via reality TV. The colony starts with 4 people and every 2 years, 4 more people join. Having babies is discouraged until after the first 5 years due to safety concerns.

Now, that means that the population size when breeding is first "allowed" is only 8. Doesn't that mean founder effect is HUGE? Now, there's horizontal gene flow every 2 years (4 more people arrive). Is this rate of horizontal gene flow enough to offset the genetic drift and founder effect?

8 or 12?

 

the 1st year they are 4

the 2nd year they are 4

the 3rd year they are 8

the 4th year they are 8

the 5th year they are 12.

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I am sure the commander would change the rules after 6 months.

[ydoaPs]

It is a bottleneck.

 

 

8 or 12?

 

the 1st year they are 4

the 2nd year they are 4

the 3rd year they are 8

the 4th year they are 8

the 5th year they are 12.

 

 

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I am sure the commander would change the rules after 6 months.

I'm not sure that changes the result of the genetics that much.

[jp255]

 

It is a bottleneck.

I'd consider this type of event to be a founder event rather than a bottleneck event. I think bottlenecks are when the population falls dramatically from deaths, and the Mars colonisation scenario is best described as emigration/reproductive isolation which is called a founder event.

 

 

I'm not sure that changes the result of the genetics that much.

Doesn't change the outcome (Aliens from the film Mars Attacks!). The populations will go their separate ways.

Edited January 29, 2013 by jp255