
Choosy Eggs May Pick Sperm for Their Genes, Defying Mendel’s Law - sprucely
https://www.quantamagazine.org/choosy-eggs-may-pick-sperm-for-their-genes-defying-mendels-law-20171115/
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chiefalchemist
Does this (read: could this) help explain why some couples have problems
conceiving? Perhaps, at least in some cases, the egg is saying, "no way
buddy."

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Alex3917
> Perhaps, at least in some cases, the egg is saying, "no way buddy."

Assuming this is true, it would be happening in less than 1% of cases (given
the prevalence of male-factor infertility and the prevalence of its known
causes). So if such an ability exists, it doesn't seem to be getting used very
often. Which, given the evolutionary complexity that would be required to
evolve such a system, seems surprising. So my guess is that either that's not
a thing, or else it exists only as a failure state of some other mechanism
rather than as something that has evolved to directly confer some sort of
reproductive advantage.

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gjjrfcbugxbhf
I thought that partner incompatibility was extremely common?

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caio1982
Just incompatibility, without the partner. Fluids pH problems are much more
common than you'd think, and it has nothing to do with the partner (besides
being treatable). And it's just one of the many problems that may occur, but
none of them is like a partner issue because your bodies don't "match".

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chiefalchemist
Yes. But if the egg is making a decision can't other parts of the process, at
least in theory, be serving as gate keepers as well? Thst is, it's not just
the egg being selective. Selective is baked into the recieving organism (i.e.,
the human female).

To me that doesn't sound too far fetched and to some extent makes perfect
sense.

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avdempsey
Cool to seen this on HN; my wife did the illustration for this article!

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caio1982
She did a great job!

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cwkoss
Reminds me of the CS problem: write a program which prints out its own source
code.

But way more impressive. How can a cell with a single strand of DNA 'decide'
which copy of a gene is a mutation? Or do eggs just bias for sperm with more
genetic differences?

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vikiomega9
These decisions interface via binding sites[1] which can be thought of as
having "bias".

[1]
[https://en.wikipedia.org/wiki/Binding_site](https://en.wikipedia.org/wiki/Binding_site)

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sjg007
If I understand correctly, they see associations of alleles in the zygotes
that suggest the gametes have not paired randomly.

Basically it could be that the egg and the sperm have different proteins
expressed on their cellular surfaces which go together like a lock and key and
may also function as attractors ( chemical sensing or something).. all of this
would originate from genes in the gametes.

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rllin
I feel like this is a misunderstanding how strict Mendelian genetics is.

Most evolutionary theorists think more like physicists and do realize every
trait is selectable.

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gewa
This... Mendel's law is only applicable to a really small hand full of traits.

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dekhn
Try saying that around a geneticist :( most i know consider mendelian genetics
to apply to everything and nearly all traits/phylogenies are considered
monogenic.

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klmr
You hang out with the wrong geneticists. Most do _not_ consider most traits to
be monogenetic. It’s just vastly easier to focus on them when doing research.
But the field as a whole has long since accepted that most interesting traits
aren’t Mendelian. The whole field of GWAS and (e)QTL studies is founded around
that recognition, and virtually all modern genetic models assume at least an
additive effect of (known and unknown) variations as contributors to a given
phenotype (and have, for a very long time).

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gowld
Did they rule out the possibility that the mutant gene they put in the male
mice caused the sperm to be bad at sperming?

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psloth
"Perhaps, Nadeau reasoned, the problem lay in the sperm, not the egg. He
therefore bred male mice with and without the mutation to healthy mutation-
free females and found no differences in the males’ fertility"

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sjg007
I thought there was evidence that the female immune system also "selects"
against some sperm as well.

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mozumder
This probably answers a question I have about genetics - that there just isn't
enough variety if reproduction was random.

Genetic differences that have no bearing on survivability, like skin patterns
or colors or whatever, should be widespread through every species, but they're
not.

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andai
That's really interesting to think about. Somewhat related, I asked a
geneticist once why there was so much diversity in humans vs pigeons which all
looked the same to me.

He said, "We're tuned to notice differences between people, not pigeons.
Perhaps we all look the same to them!"

Perhaps there is precisely this sort of random variation in the differences we
_don 't_ notice, because by being oblivious to them they are not sexually
selected for or against?

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rsynnott
If anything, humans have abnormally _small_ genetic diversity; most species
have more. We went through a population trap at some point in the past, and
nearly went extinct; we probably lost most of our diversity then.

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rscar
Don't be surprised if Todd Akin comes out of the woodwork to say he was right.

i.e. Mr. "It seems to be, first of all, from what I understand from doctors,
it’s really rare. If it’s a legitimate rape, the female body has ways to try
to shut the whole thing down."

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m3kw9
It would make evolutionary sense to have the ability to select better sperm.

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gweinberg
It could if the egg could somehow know which ones were better. But how could
it know that?

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m3kw9
Probably some sort of gene expression

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graeme
I thought the standard view was that eggs did some selecting. At least, that’s
what I gathered by reading about IVF and birth defects.

I can’t find a specific reference offhand though.

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biomcgary
The current evidence is inconclusive, but many obvious alternatives have been
ruled out.

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pishpash
Furthermore, if true, it shouldn't be overly surprising, since gametes are
another stage in the life of an organism with great selection pressure. Why
assume it behaves randomly?

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virmundi
No known sense organs to pick another environmental benefit. Classic biology
assumes such a means to respond by selecting in this case.

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phaitour
this is interestingly in line with chinese traditional medicines perspective
on reproduction. their theory is that it’s heavily based on the receptability
of the egg and therefore it’s largely the mother who’s largely in control of
things like gender selection. things like eating more acidic or basic foods
affect the environment for the sperm to swim in and even the month of the
mother’s life has an effect on what the egg would choose.

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amelius
Not a biologist, but wouldn't an alternative hypothesis be that the DDX1 gene
somehow affects the sperm cell's physical abilities, e.g. motility?

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skate22
So... we are the chosen ones?

