I was reading about recessive and dominant alleles, say blue and brown eyes as per Mendel's theory.
Let's assume that Blue eyed have an evolutionary disadvantage and that over a period of time they become extinct. The last of the blue eyed people die without offsprings.
Now the remaining people with brown eyes still may have the recessive blue eye allele. Two such people having the blue allele could give birth to a child with blue eyes and the extinct blue eye could reappear again. Unless the blue allele itself disappears there is a possibility for the blue to manifest itself.
Does this mean that Extinction cannot happen unless the said allele disappears completely?
Extinction of the dominant allele, brown, is simpler to understand. If the last of the brown eyed person dies without offspring then all the remaining population will have only blue eyes. Since blue is recessive, all the blue eyed people will have to have both alleles blue. Hence brown cannot reappear except in the case of a mutation creating a brown allele.
Does this mean that a species is more likely to become extinct only if its alleles are all or mostly dominant?
After I wrote this post, I started Googling and found some relevant links which are listed in Additional Reading below. One thing struck me as strange when I was reading some of the articles. That one should not consider that recessive allelle as being less frequent in the population, and that the word recessive should only refer to whether the allelle is visible when it combines with that dominant one. Now, statistically the recessive allele is more likely to be much lower in population (approx 25%) unless natural selection or some other reason chooses the recessive over the dominant.
Another thing that confuses me is the expression that "a success adapts to it's environment". To me, such an expression is misleading. An animal does not adapt and induce a mutation. Natural or sexual selection ensures that the "unfit ones are removed" leaving the "fit ones standing".
After I wrote this post, I started Googling and found some relevant links which are listed in Additional Reading below. One thing struck me as strange when I was reading some of the articles. That one should not consider that recessive allelle as being less frequent in the population, and that the word recessive should only refer to whether the allelle is visible when it combines with that dominant one. Now, statistically the recessive allele is more likely to be much lower in population (approx 25%) unless natural selection or some other reason chooses the recessive over the dominant.
Another thing that confuses me is the expression that "a success adapts to it's environment". To me, such an expression is misleading. An animal does not adapt and induce a mutation. Natural or sexual selection ensures that the "unfit ones are removed" leaving the "fit ones standing".
Additional reading
- https://www.reddit.com/r/askscience/comments/2h42n3/can_recessive_genes_eg_blue_eyes_blondred_hair/
- https://www.reddit.com/r/askscience/comments/58nav8/can_dominant_traits_disappear/
- https://davidson.weizmann.ac.il/en/online/askexpert/redheads-%E2%80%93-endangered-species: This article expresses the same view that I mentioned.
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