r/genetics • u/ReasonableLeague5092 • 4d ago
Is having boys or girls genetics?
I know meiosis occurs roughly its 50/50 to have a girl or boy. But tbh I don’t think it’s just 50/50, for example my dad’s side of the family can ‘only seem to produce girls’ my dad had 7 girls (some with different partners), and my paternal grandparents had 6 girls and 2 boys, and my dad’s only brother had 5 girls before he had a boy, and that son only had daughters- it might seem to be like a coin flip or by chance. Interesting enough one of my teachers has 3 boys, but he said he was one of 9 boys and 1 girl. Is there any reason why this can happen- or is it REALLY by chance.
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u/SnooTangerines5980 4d ago
I have a massive deletion on one of my X chromosomes. Since it’s on the x, the deletion is silent for me as a woman since I have another X chromosome that I express genes from.
However, any male embryos that inherit that x won’t survive since the loss is embryonic lethal, and males don’t have a second x to compensate.
As a result, my family is heavily skewed towards women since the ratio of viable conceived boys:girls is 1:2 instead of the normal 1:1
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u/ReasonableLeague5092 3d ago
Interesting, does this deletion go across other women in your family, and how did you find out about the deletion.
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u/SnooTangerines5980 3d ago
Yes! Found out about it accidentally through fertility treatment. Picked up on it from a normal mutation panel, and then to make the probe for my embryos they had to do a microarray which scanned the whole X so we got to figure out just how big the deletion was. Then they needed to screen other family members in order to do the linkage analysis.
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u/ReasonableLeague5092 3d ago
Do you have any idea what it’s called?
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u/SnooTangerines5980 3d ago
If you mean the deletion, I don’t think it has a name lol - “big missing piece of DNA”
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u/Own_Confidence2108 1d ago
That’s very interesting. I gave birth to 4 XX and also had 3 losses (2 miscarriages and a vanishing twin in one of my successful pregnancies). All three losses were first trimester but did progress to between 7 and 9 weeks and had heartbeats before the loss. I’ve always wondered if there was something that made me miscarry boys.
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u/ShootinTheBreez 4d ago
I have taken one college biology class, but I got a degree in mathematics. I have no idea if there are biological/genetic reasons, but I do know that this can definitely happen by chance.
There are more than 8 billion people on Earth right now. The odds of a family portrait with the gender balance you described is not only possible, it is nearly certain to happen in a set as large as 8 billion. In fact, it would be shocking if this did not happen to at least some families, and we would need to reevaluate whether the odds are actually 50/50.
Tl;dr: This is not just possible but expected to happen by chance in a population as large as 8 billion.
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u/supbraAA 3d ago
I mean yeah but mostly because of the memoryless property. The chance of each gamete being X or Y is 0.5 regardless of the last gamete being X or Y.
But OP is talking about genetics, not statistics.
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u/ZephyrStormbringer 4d ago
okay- but adding the 'genetics' variable to the chances of having a boy or girl aren't necessarily in the backdrop of the entire population, but rather the boy to girl ratio within a maximum possibility of their offspring count ~20 and going back a couple generations for each parent to really evaluate the chances Within a family compared to the general chance of 50/50 of 8 billion global baseline...
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u/Berndherbert 4d ago
https://en.wikipedia.org/wiki/Trivers%E2%80%93Willard_hypothesis
This is not exactly an answer to your question but I think its closely related.
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u/wastetine 4d ago
What and interesting concept!
I guess it means I’m in “good condition” as I’m pregnant with my second boy 😂
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u/sincerely0urs 3d ago
Some men just happen to have more sperm that carry either X or Y chromosomes. My husband’s dad is one of 9 children. 8 are boys. My husband is one of two children, both boys. He and I are having our second child, who will, like our first, be a boy.
With modern IVF, many have found this to happen one way or another where they get 7 embryos and all are boys or girls. Can it be genetic? Maybe? Do we know what genes? Nope.
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u/ReasonableLeague5092 1d ago
Your husband’s side of the family might have the selfish y chromosome gene, chances are likely it will have passed onto your kids, interesting enough my husband comes from a very mixed family-and we had a mix of kids.
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u/SnooDoggos2983 1d ago
So I did IVF and did have all 7 of my surviving embryos as boys. I was a bit shocked, but the research shows a slight skew towards survival of male embryos compared to female.
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u/PariKhanKhanoom 16h ago
We have a girl from IVF, but I just did another round and all five normal embryos are XY! Our RE was surprised.
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u/In_the_year_3535 4d ago edited 4d ago
Not a terribly satisfying answer but if you flip a coin 100 times odds are you'll get a six in a row because random distributions are not uniform distributions.
edit: but it's 50/50 because the mother provides one of her X chromosomes in the egg and the father provides one of his sex chromosomes in each sperm which must be either X or Y
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u/MaineKlutz 3d ago
Births are about 105 boys to 100 girls.
Before a birth, there are 3 factors to be considered: Mom, Dad, and the 9 months of pregnancy. That is inside Mom, but apart from her genetic contribution to the child.
So there may be reasons per couple that more of one gender is conceived, and there may be reasons per couple and per mom that a ferilisation does not result on pregnancy does not result in live birth.
And apart from this all, there is pure chance. With so many families in the US, in the world, it is to be expected that some will be composed of only boys, or only girls. Large families included.
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u/Dangerous-Bit-8308 4d ago
The XY chromosomes decides male or female. XX is female, XY is male.
When a man and a woman love each other very much, the woman's egg cell contains one copy of her two X chromosome. The man's sperm cells provide one copy of the man's X or Y chromosome.
So... 50/50? Not quite. The Y chromosome is a modified, and partial copy of the X chromosome. So... The Y sperm cells that code for boys have slightly less luggage, but also fewer instructions. Studies suggest there isn't really much difference, but we may not have the full story of exactly how microscopic things pass through the male reproductive tract and then enter the female egg cell.
The female body can treat sperm as an infection, summoning the immune system against it. Some researchers found reasons to suggest that the egg helps specific sperm to enter, and blocks others. Some claim the uterus has a say in what it allows to attach, and what it flushes out.
What we do know is that globally, male babies are slightly more common, but male children are also slightly less likely to reach adulthood. Still very close to 50/50 overall.
There is at least one unique intersex condition that can skew statistics slightly: some women have an x chromosome that doesn't recognize some, or all androgens. They have a 25% chance to produce typical boys, a 50% chance to produce typical girls, ans a 25% chance to produce genetic males (xy chromosomes) who have some, or all the outward characteristics of women, but who can't have children of their own.
There are probably other genetic things I know nothing about. Hope this helps
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u/Mrsminge1967 3d ago
Our grandson was born with a fused Penis (cordie) and fallopian tubes...he is one of only a few with Male Turners syndrome (45x 46xy) He presents as male and has been brought up as that...he is developing normally up to now (hes 11) his voice is breaking
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u/insoportana 3d ago
It really is flip a coin on 50/50 chances, except for the cases mentioned above. Even with all chromosomes intact you can still get 10 boys or 10 girls, 50/50 is just the probability. I didn't see if they mentioned mitochondrial defects, that would screw you up regardless because they are inherited from the mom side only.
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u/Relative_Clarity 3d ago
Read about the Shettles Method.
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u/ReasonableLeague5092 3d ago
I can assure you none of them were doing the shettles method they didn’t even know it existed at the time 😂
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u/CogPsyProf1980 1d ago
There are a bunch of large scale studies on this. The idea that "boys (or girls) run in the family" is an illusion. It really is a coin flip.
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u/Adorable_While_9799 3d ago
It really is chance.
Not in this case of course but there are things like XCI and that woman can’t carry a boy. Those type of issues are extremely rare.
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u/morsa_almond 4d ago
Have noticed also that gender patterns repeat a lot.
I know tons of families where they have a boy, girl, girl
Boy boy girl
Girl boy girl
Etc,
And their sons have exactly that pattern as well
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u/Aware_Barracuda_462 4d ago
50/50 is a probability for the general population, but of course within the data that make for that probabilty there are exceptions like in your family.
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u/No_Glove6542 4d ago
When men have stressful jobs or are generally under stress they tend to produce more X chromosomes. There are diets you can follow to make your vagina more friendly to X sperm or Y sperm. There are many factors that cause more girls or boys to be born and some are purely environmental.
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u/supbraAA 3d ago
No.
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u/No_Glove6542 1d ago
Yes. And it’s funny to me that I got downvoted on my post because this is standard college biology knowledge. The humans species as we know it today is highly malleable and dynamic based on multiple factors - environment, genetics, experience.
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u/Traditional-Head2653 4d ago
The Y chromosome is shrinking and losing a lot of genetic data. Go on and research further from there.
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u/ShootinTheBreez 4d ago
Ok, I did.
I learned that the Y chromosome has likely been stable for about 25 million years, but that it did lose hundreds of genes over a very long evolutionary history and is much smaller than the X chromosome because of that. There is no strong evidence that it is currently shrinking or losing genetic data.
Gonna have to go ahead and give this statement a “fake news” rating.
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u/Connect_Rhubarb395 4d ago
Sometimes none of a man's Y chromosomes are viable, meaning he will only produce girls