• Question: Has anybody ever been with 2 extra chromosomes?

    Asked by cjlynd2019 on 18 Jun 2019.
    • Photo: Kaitlin Wade

      Kaitlin Wade answered on 18 Jun 2019:


      Individuals with 2 extra chromosomes are very rare. Trisomy is a condition where individuals are born with one extra chromosome and are viable (able to survive) so are born but some have developmental problems. For example, people with Down’s syndrome tend to have an extra chromosome 21. But, apparently, ~15% of miscarriages have some element of trisomy. When there are two extra chromosomes, this is called tetraploid, which sources tend to say that this is not compatible with life. But apparently, tetraploidy is observed in about 1–2% of early miscarriages and it’s not clear whether these tetraploid cells are viable.

    • Photo: Rebecca Moon

      Rebecca Moon answered on 18 Jun 2019:


      Yes it is possible but very rare. The usual chromosomal configuration is 46 (23 chromosomes in pairs) XY for a Male and XX for a female. I once looked after a little boy who was 46 XXYY, so he had an extra cope of both the X and Y chromosome. It resulted in short stature, infertility and learning difficulties.

    • Photo: Nina Rzechorzek

      Nina Rzechorzek answered on 18 Jun 2019:


      Excellent question; someone being born with two extra chromosomes in every cell is extremely rare (see 48,XXYY syndrome below). However, various cancers can contain cells with various forms of aneuploidy (abnormal numbers of chromosomes), even though the rest of the healthy cells in that person’s body contain a normal number of chromosomes.

      48,XXYY syndrome is estimated to affect 1 in 18,000 to 50,000 males and results from an extra copy of both sex chromosomes in each of a male’s cells (48,XXYY). Extra copies of genes on the X chromosome interfere with male sexual development, preventing the testes from functioning normally and reducing the levels of testosterone. Many genes are found only on the X or Y chromosome, but genes in areas known as the pseudoautosomal regions are present on both sex chromosomes. Extra copies of genes from the pseudoautosomal regions of the extra X and Y chromosome contribute to the signs and symptoms of 48,XXYY syndrome; however, the specific genes have not been identified.
      This condition is not inherited; it usually occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. In 48,XXYY syndrome, the extra sex chromosomes almost always come from a sperm cell. Nondisjunction may cause a sperm cell to gain two extra sex chromosomes, resulting in a sperm cell with three sex chromosomes (one X and two Y chromosomes). If that sperm cell fertilizes a normal egg cell with one X chromosome, the resulting child will have two X chromosomes and two Y chromosomes in each of the body’s cells.
      The above information was found at these very useful websites, which cover what we know about 48,XXYY syndrome and some other chromosomal disorders:
      https://ghr.nlm.nih.gov/condition/48xxyy-syndrome
      http://www.geneticdisordersuk.org/gduknetwork/48xxyy
      https://ghr.nlm.nih.gov/primer/mutationsanddisorders/chromosomalconditions

    • Photo: Ross Hill

      Ross Hill answered on 19 Jun 2019:


      Yes! And it’s not good for you.

      The squad have done some great research so read their answers!

    • Photo: Kate Timms

      Kate Timms answered on 19 Jun 2019:


      Hi! Yes, it is possible. As other have explained, having extra chromosomes results in disabilities and disorders which can affect everything from your physical appearance (i.e. making you shorter or have specific facial features), your health and your mental abilities. Being born with 2 extra chromosomes often makes this even more severe, as the others have talked about.

      Interestingly, lots of cancer cells have more than one set of chromosomes. We call these polyploid. It’s also really common in healthy plants.

    • Photo: Matthew Bareford

      Matthew Bareford answered on 20 Jun 2019:


      Certainly possible, as others have already pointed out with some great answers!

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