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Can recessive alleles be eliminated from a population?

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Postby Jelanen » Wed May 04, 2005 9:41 pm

Yes, you could eliminate the a allele but only under the following conditions:
1. That the AA allele confers a greater chance of survival than Aa heterozygotes. If Aa heterozygotes have an equal or greater chance of survival then you won't ever eliminate the a allele.
2. You give it a lot of time and many many many generations. The amount of time required is a function of the first condition and exactly how detrimental the recessive allele is in the heterozygote.

QED

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Postby cytochromeP » Thu May 05, 2005 3:13 pm

Jelanen wrote:Yes, you could eliminate the a allele but only under the following conditions:
1. That the AA allele confers a greater chance of survival than Aa heterozygotes. If Aa heterozygotes have an equal or greater chance of survival then you won't ever eliminate the a allele.
2. You give it a lot of time and many many many generations. The amount of time required is a function of the first condition and exactly how detrimental the recessive allele is in the heterozygote.

QED

-Jelanen


1. The question asked does'nt say anything about relative survival ability of AA and Aa. Hence it is to be taken granted that they are 'equals'.
2. Initial pupulation has 50%Aa, 25%AA, and 25%aa. Of these aa woud'nt survive to have any progeny and hence can be neglected. Thus now, Aa heterozygotes wud effectively constitute 2/3rds of the population. Now, two Aa heterozygotes mating with each other is more probable than two AA homozygotes mating with each other.
Therefore, the next generation wud contain some aa homozygotes, which wud of course die away without procreating - but the bottomline is - these aa homozygotes wud exist nevertheless.
...and so on NO MATTER HOW LONG YOU WAIT (until BIG Crunch,atleast :D )
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Postby MrMistery » Thu May 05, 2005 6:31 pm

Read Jelanen's post carefully
If Aa heterozygotes have an equal or greater chance of survival then you won't ever eliminate the a allele.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
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Postby cytochromeP » Fri May 06, 2005 3:35 am

MrMistery wrote:Read Jelanen's post carefully
If Aa heterozygotes have an equal or greater chance of survival then you won't ever eliminate the a allele.


I did.
There r no "if"s in the Question posted. It is granted that AA and Aa are equals when it comes to survival and passing on your genes to your progeny.
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Postby Jelanen » Fri May 06, 2005 3:59 am

My answer is 100% correct and would have not only answered the question correctly would also have (and does) shown a further mastery of the material being tested than just a simple "No". It was beat into my skull throughout college that one word answers are unacceptable. You are correct that no information given in the question regarding the relative survival suitabilities of the homozygous dominant and the herterozygote, but that does NOT permit the assumption that they have equal chances. What it does allude to is that it would be in your best interests to cover all the bases, especially since the question asked if was possible. Therefore my statement presented the conditions that would allow for the recessive allele to be lost from the population. Also, my statment is structured as an IF/THEN statement and if the IF part is invalid then so is the THEN statement. Either way I'm right, my butt is covered, and I get full credit for the question (and hopefully some brownie points with the prof to be used later when requesting letters of recommendation :D ). And thats about all the trashing of my answer I'm going to tolerate.

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Correction

Postby cytochromeP » Fri May 06, 2005 4:27 am

mithrilhack wrote:They're probably talking about the hardy-weinberg principle in which the case is it won't be unless there is outside intervention(a shotgun).


I guess mithrilhack amongst all of us was the one to have come any closer to the real answer.
It does indeed involve the Hardy-Weinberg equilibrium. Please take a look at the foll. : http://anthro.palomar.edu/synthetic/synth_2.htm (last paragraph)
It has been asked whether "Can recessive alleles be eliminated from a population?"
But rest of us were focussing on elimination of individuals (aa) !
According to Hardy-Weinberg Principle the ''allele frequencies will remain unaltered indefinitely unless evolutionary mechanisms such as mutation, natural selection, and non-random mating cause them to change".

This phenomenon I must add is more a manifestation of nature being governed by mathematics rather than biology.
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Postby mith » Fri May 06, 2005 5:14 am

I like your spunk jelanen :D
Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
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