help me understand mutations Veeky Forums
if blue eyes mutated for the first time ever in modern times even if the guy who had them had 10 children wouldn't the mutation disappear within a few generations and "regress to the mean" so to speak of non blue eyes? do mutations require a high degree of inbreeding to be maintained? are mutations always passed on?
thanks
>require a high degree of inbreeding to be maintained
Yup. What usually happens is a family or small group moves to a different area of the world that geographically isolates them, and they turn around and have sex with each other so any traits they have that may make them differ from the rest of the population in the world becomes more pronounced over time rather than being a one time anomaly
Not necessarily, since something like blue eyes isn't detrimental there's no reason for it to be selected against, so I see no reason for it to drop out, in fact: if someone has gene for blue eyes and then has 10 kids we'd expect about 5 of them to also carry the gene for blue eyes.
Isn't it 1/4, or 2 of them, actually?
Bb/BB/bb/bB?
>wouldn't the mutation disappear within a few generations and "regress to the mean" so to speak of non blue eyes?
yes, that's entirely possible
>do mutations require a high degree of inbreeding to be maintained?
it's much easier in general for a mutation to become fixed in a small population. that can mean it spreads to everyone in the population or it dies out immediately. large populations fix much more slowly
>are mutations always passed on?
no
I was under the impression that there was only one person with a gene for blue eyes, so BB/BB/Bb/Bb, so 5 would have the gene for blue eyes and that's how it would propagate in a population.
We know for a fact that the mutation that caused the phenotype for blue eyes appeared in central/northern Europe around 10 000 years ago. We still don't know if the phenotype was expressed or not.
Anyways, yes, for the mutation of a recessive gene to be expressed, there must be inbreeding. Of course, there's always the possibility that there were more than two individuals who randomly had the same mutation, but this is very improbable.
My theory on that subject is that the first individual who had blue eyes was chased away from his tribe and ran away to the north. Since a lower amount of melanin in the region of the eyes is related to the amount of melanin in the skin. Its probably that this individual also had lighter skin. The lighter skin gave the opportunity to get more vitamin D from the sunlight, which was lacking in the individuals with darker skin (they probably got rickets from the lack of vitamin D). Since the people of dark skin were dying at a higher rate than the people of lighter skin pigmentation, the gene that opened the door to a lower concentration of melanin was passed on more.
Just a theory
The original mutation would not have been expressed. It would have been generations after the blue eye mutation occurred before the first blue eyed person was born
All blue eyed people are directly descended from the same individual
Who said it wasn't expressed though? I haven't found a source saying so back when I was doing a paper on this subject. It would clear a lot of possibilities.
Because it cant have been. Its a recessive gene and the original mutant would have had a functional allele
Unless somehow both alleles mutated at the same time independently to produce the same genotype. Which is absurd
>All blue eyed people are directly descended from the same individual
That depends on how common the mutation is. It's possible that the gene for eye color is highly susceptible to mutation and therefor could have occurred multiple times throughout history.
This is the mistake people usually make in the specific subject. The thing is, the mutation occurred on a gene that affected another gene that had a function in the production of melanin, not the gene corresponding the phenotype of eye color. It wouldn't be surprising if the first individual simply had a lack of melanin in his body that affected the pigmentation of the eyes.
Theres only one blue eye gene as far as i'm aware, which suggests it only emerged once
You have to have a specific mutation on both chromosomes to have blue eyes. There is no believable way the original mutant could have had this
>what is selection
What I find interesting is that blue eyes didn't really depend on climate.
Northern people of Siberia and the Americas never evolved the trait, only northern people of Western Eurasia did.
Not true.
Rare recessive traits are hidden in heterozygotes. While they usually disappear over time they can persist for a very long time by chance or based on the number of offspring those heyerozygotes have.
That's why beneficial recessive traits take a long time to accumulate in a population initially- because they aren't expressed
mutations are random
blue eyes could have just as easily sprung up in africa
What I'm saying it that, the mutation in question happened on gene that changed the phenotype of eye color, which would mean that it's b/b.
If the mutation occurred on the alleles of the gene related to the eye color phenotype, then of course the dominant allele of brown eyes would've been expressed. But it's just not the case.
Concerning how the gene for blue eyes spread, I believe it's due to a mix of migration and strangling of the gene pool. The circumstances in northern Europe favored a lighter pigmentation of the skin, which is usually followed by a lighter pigmentation of the eyes.
Basically, inbreeding until everyone has light skin and eyes pigmentation.
>mutations are random
no
mutagens exist
radiation also induces mutation
Correct me if I'm wrong, but I'm pretty sure the inheritance of eye color is polygenic. You can't express the inheritance through simple monohybrid crosses as this assumes the inheritance is based on two alleles, B and b.
The result of the mutation is random, the drive for mutation is pretty constant over several generations. Is that what you're saying?
>You can't express the inheritance through simple monohybrid crosses
You can, since the B allele is dominant over the b allele. This means that an heterozygous individual will only have the dominant allele expressed, but can still pass on the recessive one. This is why couples with brown eyes can have children with blue eyes.
B/B, B/b and b/B is brown
b/b is blue
Yes but you are implying there are only 2 observable phenotypes for eye color, which is wrong. Eye color is not a Mendelian trait.
Its true that there are more than two possible phenotypes, but all those phenotypes are decided by only two alleles, it's allele1/allele2, no more. The blue or brown eyes was just an exemple, I could have chosen G/b and it would've been green.
Alpha centuri?