Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Greater likelyhoods of having 2 children of the same gender than 50%?

  1. Aug 10, 2004 #1
    A random little observation I've made is that people I know who have 2 children, will more often than 50% of the time, have 2 children of the same gender. Is there any pre-disposition to this, or are my observations just randomly leaning that way and there is no sort of trend among humans that sets of 2 children are more often than not of the same gender? I was thinking perhaps that some men produce more X or more Y sperm, and that there's a greater likelyhood of the sperm which impregnates the ovum being X or Y, but I have no idea whether this is the case.

    Anyone want to shed some light on this?
     
  2. jcsd
  3. Aug 11, 2004 #2

    Moonbear

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    This news article (a bit old) seems related to the topic.
    http://www.theeagle.com/health/breakingnews/041902infantgendersmokers.htm

    I'm going to have to bug my friend who works in an IVF clinic about this. I had heard years ago that there is a reason why some couples have lots of girls and others lots of boys, and that it's not truly random but has something to do with genetics, but I don't remember if I was given a good explanation or what it was. I've never looked into it beyond that.
     
  4. Aug 12, 2004 #3

    Monique

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Wasteofo2: when the children are the same gender, are they more often female than male? It could be a X-chromosome gene.

    Maybe it's the hormonal environment of the mom that inhibits the normal development of one sex.
     
  5. Aug 12, 2004 #4
    Do you mean something that would stop Y sperm from entering the egg? Or that would abort the egg very early?
     
  6. Aug 12, 2004 #5

    Monique

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    That would cause it to abort. Think about wrong imprinting in females (I believe it has a different name) or about a mutation in a gene that causes complete loss of function in the male.
     
  7. Aug 12, 2004 #6

    Moonbear

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Though, I suppose it could also be possible that something could be wrong with the sperm themselves to prevent them from entering the egg. Perhaps a defect in the acrosome reaction?
     
  8. Aug 12, 2004 #7

    Nereid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Is there any observed pattern for non-identical (fraternal?) twins (other than what you would naively expect)?
     
  9. Aug 12, 2004 #8

    Monique

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You're suggestion there might be a gene located on the x or y chromosome involved in the process?
     
  10. Aug 12, 2004 #9
    Remember Henry the 8th (I think?) He tried so hard to have a son, but he couldn't. He kept getting new wives thinking the female was at fault. He had like 6 wives, and I'm guessing a handful of kids, and only one son.

    Is it really possible that some gene or something on the male sperm would cause the egg to abort? What kind of stuff would cause the egg to abort?

    The acrosome reaction, that's right when the sperm binds the egg, right?
     
  11. Aug 12, 2004 #10
    I talked to a reproductive physiologist about this, just for a few minutes. She said in some animals the female can "choose" which sperm to "accept" (like in animals with multiple fathers, like if there is more than 1 animals sperm in the female, the female could pick the highest quality sperm).

    And, sometimes males can produce mainly male or female sperm.

    I guess it seems that there are a multitude of factors:

    1. Males producing more of one sex sperm than the other (perhaps such as Henry the 8th).
    2. Females eggs being "selective" on the sperm sex (how would they fight it off? How would it abort the fetus?)

    She said how the sperm is deposited into the vagina, and the "gel" of the semen breaks down and causes the uteris to contract which aids in getting the sperm to the egg. Is it possible that poor quality sperm wouldn't cause the uteris to contract? Or could the male, when producing sperm, say his "female" sperm, when the oxytocin (??) that causes the contraction could be not added properly so that one sex sperm would tend to not cause uteris to contract?

    Interesting topic..
     
  12. Aug 12, 2004 #11
    Monique, I have not noticed that more often tha not pairs of children who are the same gender are female, but I generally associate with males more than females, so I can't really tell.

    Does anyone know how the chromosome of a sperm is determined? I had always thought that you have the spermatocyte whichhad 46 chromosomes, it split, one half had an X, one half had a Y, then they duplicated themselves, and split, creating 2 cells with X and 2 cells with Y chromosomes, but perhaps that's not how it is.
     
  13. Aug 12, 2004 #12

    Kerrie

    User Avatar
    Staff Emeritus
    Gold Member

    i have two children, one of each gender...when i wanted a second child, i wanted to try for a male, since my first was female...i read that i should eat a lot more meat and vegetables as this had an effect on the uterine chemical makeup (acid vs base) in "selecting" the male sperm-sure enough my second was male...interesting to note that prior to me becoming pregnant with my first child (a daughter), i endulged in more sweets and carbs prior to her being conceived...i couldn't find any backup on this, maybe monique can?

    what i had read was that a more acidic uterine environment killed off one type of sperm and a more base uterine environment killed of the other...as they say, you are what you eat :biggrin:
     
  14. Aug 13, 2004 #13
    Interesting. It's weird how us humans have to be told these things, but other "less intelligent" animals just "know" it. Like how dogs know to eat grass when theri stomach is upset. Weird!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Greater likelyhoods of having 2 children of the same gender than 50%?
  1. Twins have same DNA? (Replies: 4)

  2. Gender genes (Replies: 15)

Loading...