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twins...

  • 22-12-2007 4:54pm
    #1
    Will
    Closed Accounts Posts: 19,183 ✭✭✭✭


    I have a friend she is a twin. Nothing out of the ordinary there, she showed me a pic of her sister and she has down's syndrome. How rare is it for something like this to happen?

    Where one twin is fine and the other has a intellectual disability?
    Just puzzled by it all really, was checking wikipedia and nothing is said about it.


Comments

  • #2
    Chunky Monkey
    Closed Accounts Posts: 923 ✭✭✭Chunky Monkey


    I'm gonna take a guess here and say that there was possibly one extra chromosome between the two of them so only one of them got it.


  • #3
    John
    Registered Users, Registered Users 2 Posts: 12,135 ✭✭✭✭John


    If they're not identical twins then the odds of one having something like Down's syndrome is the same as between normal siblings (as fraternal twins are nothing except a normal brother and sister born at the same time).


  • #4
    Will
    Closed Accounts Posts: 19,183 ✭✭✭✭Will


    well yeah im aware down's syndrome is due to one extra chromosome, just strikes me as odd is all :)
    yeah ok, think il take John's anwer. il ponder about it some more


    thanks for the replies


  • #5
    Chunky Monkey
    Closed Accounts Posts: 923 ✭✭✭Chunky Monkey


    Haha you're right, John's answer was the better one :p

    Two ova released, each are separate cells. A mutation happens in one of them during meiosis and so it'll develop so that one embryo will have three no. 21 chromosomes rather than two. So only one of the twins will have down's sydrome.

    I wonder have there ever been Down's syndrome identical twins. I mean children who have Down's syndrome usually have older mothers and older mothers often need IVF treatment to have kids. Unless it only happens when fertilisation is natural. Hmmm... Nice one wilburt that is interesting.


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