h a l f b a k e r y
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Mostly about humans, but might happen in other species, too
I have an Idea regarding human genetics that is associated with
intriguing possibility. It is possible that something that I think I
know on this subject is erroneous, which would render my Idea
unBake-able by Nature. Therefore I need to explain what I
know, in order that the
esteemed members of this site might
out any flaws --but also to explain why the Idea might make
Thanks in advance for your patience in wading through the
Sometimes an ovum is constructed that contains no nuclear DNA
own. If a sperm containing a Y chromosome merges with that
ovum, the first thing that happens is, all the DNA in the sperm
gets duplicated, so that every chromosome becomes part of
However, a zygote with a YY chromosome pair is not viable,
leads to a medical condition known as a "molar pregnancy",
involving a thing called a "hydatidiform mole". Such a
must be terminated lest it cause "trophoblastic disease".
But what if the sperm had an X chromosome instead? In that
the initial duplication process should yield an XX pair for the
zygote, which has a chance of being viable, forming a normal
I fully understand that in such a case every single genetic
in all the chromosomes would be duplicated and result in a
matched defective gene-pair. An actual normal female body
from the preceding events might be extremely rare; the zygote
might not actually ever be viable enough to ultimately yield
a living female body, much less a normal one.
Still, I find the possibility intriguing, that a few women might
walking around, each of whom doesn't have any of her mother's
nuclear DNA (she will have her mother's mitochondrial DNA),
only has nuclear DNA from her father's mother. If she is
she must have a nearly defect-free gene chart!
Has anyone thought to look for that? Or found some evidence
it by accident?
Some data about molar pregnancies
This is how I concluded that the Y-chromosome got duplicated. No restrictions on duplication are mentioned. [Vernon, Feb 05 2016]
[bungston, Feb 05 2016]
||I've thought of one error, involving the fact that humans
have 23 pairs of chromosomes, and when sperm are
manufactured, the pairs are randomly broken up to obtain 23 individual chromosomes for 1 sperm. So some of that DNA comes from the father's mother, but also some of it
can come from the father's father. The X chromosome
itself is guaranteed to have come from the father's mother.
But not the others.
||Just think what this means for any woman who thinks she
has nothing in common with her mother! She might be
more right than she knows!
||// However, a zygote with a YY chromosome pair is not
viable, and leads to a medical condition known as a "molar
pregnancy", involving a thing called a "hydatidiform mole".
||Source? Wikipedia's molar pregnancy article says "46,YY
(diploid) is not observed."
||It's an interesting possibility. I work (partly) on IVF and
chromosomal anomalies, and the number of weird things that can
happen at the chromosome level is truly amazing.
||I would wager that there are some people walking around with two
copies of one of their chromosomes from the same parent.
However, whether a full chromosome set from one parent would be
viable is doubtful.
||In particular, there are epigenetic factors - for many genes, one
copy (either the paternal or maternal) is switched off while the
other is on; a doubled-haploid individual would have this system all
messed up. And, as you noted, any recessive disorders would
manifest themselves - I suspect that haploid genomes with *no*
lethal defects are incredibly rare.
||It looks like YY is not OK even for a mole. Which makes sense; a bunch of stuff is on X and only ear hair on Y. Moles are XX or, if 2 sperm team up, possilby XY.
||I'm rather concerned that this idea is not so much half baked,
as actually so perfectly baked that it produces buns of such
unqualified loveliness that all men everywhere will fight to
the death for them, resulting in total decimation of y-
chromosomes, and consequent death of the entire human
But then, some people reckon that might not be such a bad
idea. So - carry on.